Underground Marvels (2019–…): Season 1, Episode 5 - Bouzincourt - full transcript
A labyrinth of tunnels underneath a tiny French village which contains mysteries from several historical eras, and a Welsh slate mine that has been given a new lease of life.
Narrator: Beneath a tiny village,
A vast world of secret tunnels.
Oh, my goodness.
Why were they so important during
One of the world's bloodiest battles?
This is the biggest single
concentration of graffiti
On the somme.
Narrator: What unbelievable uses
Have been found for these welsh caverns...
Amazing just to think that everything
Was actually mined here by hand.
Narrator: ...Carved
out here by slate miners
In the harshest conditions.
They are razor sharp.
They would cut you in half.
Narrator: And deep beneath a glacier...
It's the most volcanically
active spot on earth.
Narrator: ...What stunning
spaces lead to an entrance
To earth's fierce and fiery core?
Wow!
Beneath our feet lie
extraordinary chambers, caves,
Vaults, and tunnels...
The span and the size is just crazy.
Narrator: ...Some designed
and built by humans,
Others formed over thousands of years.
But how were they created and adapted?
By whom?
And why?
You've got to face your fears.
Narrator: Throughout
history, subterranean life
Has captured our imagination.
We're going further and
deeper to unearth the mysteries,
The stories, and the secrets
of underground marvels.
France is the largest
country in western europe,
With its northern region
dotted by quaint farms
And small towns.
40 feet below this picturesque
village lies a complex
Of tunnels carved out
of the soft chalk bedrock.
These chambers have
protected generations of locals
And would play a key role
in one of the bloodiest battles
In human history.
The entire village would
disappear underground.
Narrator: How did the
tunnels play a crucial role
During the first world war...
It's one of those places
where time stands still.
Narrator: ...And how did they inspire those
Who sought refuge within them?
Lend some thought to him for middle earth.
♪
100 miles north of paris, bouzincourt
Is an isolated village
of around 500 people.
The church of saint honoré
dominates the surrounding
Countryside, and within it lies an entrance
To a secret world.
These tunnels contain mysteries
from many historical eras.
Battlefield expert vic piuk
has been researching these
Relics of the past.
Piuk: The first thing you
actually see here is, obviously,
A manmade structure of
bricks, but then you enter
Another world altogether.
Narrator: The villagers of bouzincourt
Started digging here in the
15th century to escape their
Harsh reality above ground.
They would've found the
porous, chalky terrain easy
To excavate by hand because it drains well
And requires no additional support.
The tunnels were built for two reasons.
They would come down
here for safety, for security,
Or to see out a particularly bad winter,
Because it's the same
temperature all year around.
It might be absolutely freezing up above,
But here it would be
actually more hospitable.
Construction started relatively shortly
After the hundred years'
war, when there had been lots
Of battles here coming
backwards and forwards.
Narrator: The hundred years'
war was a century-long series
Of battles fought between
France and England,
With the french ultimately
regaining their territory
From the british in 1453.
But there would be many more
wars in the coming centuries,
And these tunnels would
continue to give the villagers
A secret hideaway to take
refuge from the fighting.
Piuk: Incredibly, the entire
village would disappear
Underground, bringing with
them their cattle, their sheep,
Their pigs, and they
would hunker down here.
These were secret places.
As far as the enemy was concerned,
They'd find a deserted village.
The entrances would've been hidden.
Armies that passed
through this wouldn't have
The slightest idea.
Narrator: The villagers dug
out tunnels and 50 separate
Rooms to provide
accommodation for themselves
And their herds.
The largest of them covers 320 square feet.
The rooms were actually
used by individual families
In times of crisis.
There would've been a wooden door here,
Then you turned the lock on
it, 'cause it was your property.
You can actually see the wood is long gone.
You can still actually see evidence
Of where the door frame was.
This was the environment for the family.
They would've actually
lived in here and had their bits
And pieces here.
But actually, this was for the cattle.
And these were actually the
stalls for the pigs, the sheep,
Whatever beasts they
actually had down here.
Narrator: Vic is meeting local historian,
Jean luc ruvian, who has
traced his own family back
Through time by analyzing
the carvings on the tunnel walls.
[ speaks french ]
Okay. That was actually his grandfather
And his two great-uncles.
Piuk: Jean luc comes
from a long-standing family.
They've been here for centuries.
There's a long connection here.
Narrator: The most
telling carving can be found
At the entrance to one of
the underground chambers.
Right, this is the oldest inscription here
In the shelters.
Members of his family,
all those generations ago,
Slept in this cave.
This is unique.
In the year 1711, europe endured
One of the coldest winters
on record, and this graffiti is
A relic of the families who survived it.
Piuk: Almost, without a shadow
of a doubt, the entire family,
The entire village, came
down into these caves
To see out that awful period.
[ speaks french ]
He says it's a very important
place for the community
Here in bouzincourt because
it's a place that bears witness.
Narrator: Yet the tunnels
played their biggest role
In bouzincourt's history when
the tiny village found itself
On the front line during world war I.
It was a war between two power blocks,
One headed by britain and
France, the other by germany.
It lasted from 1914 to 1918.
Bouzincourt is close to
the site of one of the war's
Deadliest battles along the
course of the river somme.
Piuk: French troops are
actually in occupation here.
The somme, actually,
was a quiet period until
The battle of the somme in
1916 when the british arrived.
Narrator: The villagers
of bouzincourt fled,
Leaving the british army
to protect the western front.
And some would leave their mark
In these underground tunnels forever.
This is the biggest single concentration.
This is remarkable.
♪
♪
Narrator: During the
atrocious battle of the somme,
Soldiers fighting in muddy,
disease-infested trenches
Found these secret tunnels
hidden underneath bouzincourt,
France, as a welcome refuge,
like generations before them.
So to be 12 meters underground
in structures such as this,
Was heaven-sent for the british military.
Immediately what you see
here, it's the life of the man
Actually lived when they were down here.
Soldiers did everything down here.
Seems that this could
actually have been the chapel.
There at the back, the
earthenware jar is actually used
For rum ration.
Soldiers actually got a daily tot of rum
And it would've been very
welcome to keep out the cold.
Narrator: The battle of the
somme lasted five months
From July to November 1916.
On the first day, more
than 19,000 british soldiers
Were killed by shelling
and machine gun fire,
The largest loss of life ever
suffered by the british army
In a single day.
The tunnels provided those
brave young men with shelter
And relief from the
carnage of the western front,
As nearly three times more soldiers
Crammed into these caves
Than actual inhabitants of bouzincourt.
They left behind small
signs of their humanity
On the soft walls of their refuge.
We just see the names and
the marks they left in history.
These were real people.
These men all mattered to
their wives and loved ones.
And you could lose sight of
that, but you don't when you're
In a place like this because
you can see their names.
This is the biggest single
concentration of graffiti
On the somme.
This is remarkable.
A veteran of the great war
Said it was 90% sheer
boredom, 10% sheer terror.
These men could be here
today and gone tomorrow.
This was maybe a final chance
To leave your mark for posterity.
Narrator: There are more
than 1,500 signatures
And drawings in these tunnels that date
From the first world war.
Some, celebrities of their
time, and some who would go on
To leave a lasting impact on society.
Among the names, american
and canadian soldiers
Billeted here as part of the allied force.
There's actually two brothers
see, side by side here.
Look, can see this e.A. Jarrett
and s.H.R. Jarrett, canadians.
Narrator: Where soldiers have given their
Regimental numbers,
historians have been able to trace
Their military careers, both
during and after the war.
Ray klinsing. This guy
was from north dakota.
He won two military medals for bravery.
He survived the battle of the somme.
He actually died in 1981.
Narrator: Another carving refers to a
Particular british regiment.
One of its officers was
a celebrity at the time.
Lovely regimental badge
here of the 17th middlesex,
The die-hards was their nickname.
They were the unit that
had a certain walter tull,
Who was a pre-war
footballer for tottenham hotspur
And northampton town.
He was one of the first black
professionals in footballers,
And certainly the first
black british officer.
He was actually to die
not far from here in 1918.
Narrator: 3 million soldiers fought in the
Battle of the somme above
these very caves, and 1 million
Were wounded or killed,
making it one of the bloodiest
Battles in human history.
During one of many bombardments,
The church of saint honoré was destroyed.
It was rebuilt in 1920 in
the shape of an artillery shell
As a tribute to the fallen.
Richard stenning
recently discovered that his
Great-grandfather,
major-general william rycroft,
Was among the british
forces here over 100 years ago.
It's intriguing to come here and retrace
Some of his steps.
Narrator: Richard's here
to explore the tunnels
Where his great-grandfather
once took shelter.
♪
As a major-general,
Richard's great-grandfather,
william, would've commanded
A division of around 18,000 to 20,000 men.
There were 50 british divisions
at the battle of the somme
During this epic struggle
on the western front.
Unlike in later conflicts,
during world war I,
Senior officers still found
themselves in mortal danger
On the front line, and
william rycroft diligently noted
The trials that faced the allied forces.
That was the original, was it? Yeah.
William rycroft's account of the first day
Of the battle shows the risks that he took,
Along with his men while
around them, vast numbers
Of british and allied lives were lost.
Being the officer commanding,
you've got these lives
Of tens of thousands of
men as your responsibility.
How would I have coped with that?
Could I have stood in
his position and done that?
It makes it all real.
♪
The war devastated an entire generation,
Yet some may have found inspiration.
Also present at the battle of the somme was
A 24-year-old officer
who would go on to make
A lasting impression on the world.
There's some anecdotal
evidence that j.R.R. Tolkien
Was actually here. I saw something.
Yeah, that he served around here.
Yeah, he said he served here,
That's not open to debate.
The famous "lord of the rings" author,
J.R.R. Tolkien, undoubtedly
drew on his wartime experiences
In his epic saga of good versus evil.
Underground worlds play a
crucial role in the fantasy land
He created, named middle earth,
From the hobbit holes to the mines of moria
And the dwarven realms.
He could have very well
been in these tunnels.
It would've been very cool
to have him left his mark here.
That would've been something, yes.
Lend some thought to
him for middle earth, right?
Major operations at the battle of the somme
Ended on November 18th, 1916.
The walls serve as a lasting
memory to allied soldiers
Who stood firm in the fight
against military aggression.
These caves have offered
sanctuary for centuries,
And perhaps will continue
to do so for years to come.
♪
As part of the united kingdom,
wales is a small country
Of 7,700 square miles,
dense with natural woodlands,
Quarries, and agriculture,
and a hard-working population
Of 3 million people.
Beneath these peaks lie
natural resources formed
Over millions of years and
carved out by generations
Of workers, including young children.
What these people went
through every day just to
Put some food on the table.
Narrator: What conditions
did the workforce endure
As they mined the earth's riches?
When these pieces go, they are razor-sharp.
They would cut you in half.
Narrator: And now that its
era of heavy industrial mining
Is over, what new underground
marvel is making use
Of the subterranean spaces left behind?
Man: Whoo!
♪
Narrator: The hills surrounding the town
Of blaenau ffestiniog are
strewn with centuries of rocky
Waste material left over
from mining that defined this
Local community for generations.
Best known for its use in
roofing and flooring, slate was
First mined here by the
romans around the year 45 a.D.
But it wasn't until the
industrial revolution in the
Mid-19th century that it became
a sought-after commodity.
And for the men who extracted
it, it would be a harrowing
Place to work, with dangers
lurking around every corner.
♪
The llechwedd slate mine in wales
Extends two thirds of a mile
Under the mountainside and
contains more than 15 miles
Of tunnels and 250 chambers
spread over 16 levels.
They're accessed by a narrow gage railway,
The steepest of its kind in the u.K.
Brian jones once worked in the mine
On the maintenance
team, and is now a guide.
The world-famous slate vein was formed
500 million years ago
when this area of wales was
Beneath a prehistoric ocean.
A massive volcanic eruption
put huge amounts of heat
And pressure on the seabed,
pushing it up to an angle
Of 33 degrees and baking
it solid in the process.
During the slate mining boom of the 1880s,
The population of blaenau ffestiniog
Rose from around 3,400 to more than 11,000.
Llechwedd was one of
several mines in the town,
And miners flooded in
to work this rich seam.
Now, this looks to me
like good-quality slate.
Look at the very fine
graining in the slate itself.
Can see here where there's
been a previous miner drilling,
And you can see the blackness
in here where the gunpowder,
Where the blast has been.
Narrator: By candlelight,
men would use basic hand tools
Called jumpers to work
their way into the rock
Before setting an explosive charge
To blow away large pieces.
Brian: That's a natural crack in the rock.
A rock man would drill in here.
This depth, charge it, and blow it down.
When he blows this out,
this nice lump of slate would
Fall down here.
Up to about 1818, 1819,
this would've been done
By a jumper manually.
Narrator: By the end of the 19th century,
During the industry's peak
due to a boom in victorian
House building, half a
million tons of top-quality slate
Was extracted every year.
This was enough to produce
tiles to cover an estimated
150 million square feet of roof.
Local phil jones traces his
family connection to this mine
Back three generations.
I remember coming here
with my father and my mother.
My father always used
to say over there is where
He worked with his father,
my grandfather, in the '70s.
Narrator: Today, phil
shares the tough world
Of his ancestors with visitors to the cave.
This is where my father
and my grandfather worked.
My father was my grandfather's apprentice,
But rock men was what they were.
They would be extracting the slate.
Narrator: In 1912, drills
using compressed air
Were introduced to replace
the primitive hand tools.
Even though modern tools were brought in
To excavate slate more
efficiently, they continued
To use more familiar
methods to suspend themselves
High up on the rock face
to reach the valuable slate.
It was a death-defying maneuver.
The miners would scale
the wall using metal chains.
The reason why they used
chains was 'cause rope would
Actually rot in these
conditions eventually.
So that locks into position
and it frees my hands,
Then I can work on the rock surface.
Just move my leg like that,
and I'm out of a situation fast.
The men, they had to pay for the material
In the early days, and
what they would do is they'd
Fasten the chains to
pegs like this with fuse wire
And then they'd light the
fuse right here and they could
Get the chains back.
So they looked after
their tools and later on,
When the company paid
for the tools, they just left
These chains in place.
Don't think I could do that job.
Narrator: This subterranean
space has always attracted
Adventurers, now as it did then.
It would take a large team up to 20 years
To excavate a chamber of this size.
There's about 10 chains here.
Now, there would've been a
man on each of these chains,
So this rock face would've
been quite a busy rock face.
They would've been up
there for maybe 10 hours.
Narrator: It was a loud and
hazardous place to work.
Life expectancy of a
miner was only 45 years.
Now, you could be working
down in this chamber here,
Looking up at these
dangerous pieces here hanging
Over your head all day.
When these pieces go, they are razor sharp.
They would cut you in half.
So many men were killed down here.
♪
Narrator: After the
miners had left for the day,
Workers known as danger
men had the perilous job
Of coming in at night to
remove unstable rocks.
Brian: They would've been
working on the tops of these ladders.
Wrap your leg around the top rung,
Hang on for dear life.
Crowbar in one hand, lantern in the other.
Levering and banging
away at these pieces here,
Getting these dangerous
pieces down from here,
Making this place safer for the next day.
Now, they weren't paid
much for this job, even though
They risked their lives every day.
A lot of respect from the
men, and a lot of respect
From the management for doing this.
It's important that everybody
remembers the people that
Came here, the conditions
they worked under.
It must've been traumatic
for these young boys
Of 18 years old working down
here in the cold and the damp.
Narrator: The children,
as young as 5 years old,
Served in the mines by
chipping, washing, and sorting.
It was one of the worst
places to work if you were a kid
In the early to mid 1800s.
The mines were cramped, poorly ventilated,
And highly dangerous.
Children were in danger of
being killed from explosions,
Roof falls, or being run over by carts.
Brian: These places should be kept open
As long as possible.
The people can reflect
when they come down here.
♪
♪
Narrator: On the other
hand, the safest and most
Lucrative job at the mine
happened above ground.
Richard roberts began
working in the slate mine industry
When he was just 15 years old in 1945.
His job was to create tiles,
Which involved more skilled labor.
There you go.
Now it's the ideal size of a roofing slate.
This is where they made the wages.
These men up here actually made money.
The men underground didn't as such.
Narrator: When slate mining began here,
It produced 90% waste,
which can be seen strewn
All over the hillsides in north wales.
But with better machinery
in working mines today,
Waste is only 10%.
There you go.
The finished slate would find its way
To the docks in liverpool
before being shipped
All over the world.
The mine finally closed
down in the early 1970s
As competition from
overseas imports increased,
Making way for a modern-day transformation.
After lying dormant for
several years, developers saw
The potential for a
whole new lease on life.
When part of the mine
was reopened for tourism,
Visitors were able to
follow in the footsteps
Of the men who shaped this countryside.
And in recent years, these
worlds that once spelled danger
Have been transformed for
some rather unexpected use,
Including the creation
of an unlikely delicacy.
Narrator: The unique environment
of the slate caverns in wales
Is the ideal place for
an unexpected delicacy.
In an area of the mine
not open to the public,
An award-winning cheese is now produced.
When it's at 11 month old
and it's stacked on the shelves
Here for three months, and
then carried back upstairs
To creameries to be cut and sold.
Narrator: As a quality manager
for south caernarfon creameries,
Shon jones is keenly aware of how difficult
It is to find the right place
to store 50 tons of product.
Shon: Bringing the cheese
down here where the atmosphere
And temperature and the
pressure down here gives it
A unique, intense flavor to it.
Narrator: 500 feet below
the surface, a cavern originally
Excavated in 1856 for creating
rooftops is now packed full.
Shon: If the temperature was
too low, then the cheese wouldn't
Move on, they wouldn't mature,
Go through the maturing process.
So this is extra mature
cheddar now ready to go back
To the creamery, so what I'll be doing now
Is checking this cheese
for the flavor and the profile
Before we take it back.
This stuff's good to go.
Narrator: Each day, a
ton of cheese is brought up
And down on the vertical
train originally used
For hauling slate.
Yet an even more surprising
new use of this subterranean
Space can be found elsewhere
in the caves, inspired by
The harrowing work of the miners who hung
From the ceilings years ago.
Carwyn: The first time I came
down, I was just blown away
By the sheer size of the chambers.
Just to think that everything
was actually mined here by hand
And taken out by hand is just amazing.
Narrator: In 2014, the
world's first underground
Trampoline park opened inside the caverns.
It's a shocking transformation
from the dangerous world
In which children once labored side by side
With their fathers.
It's like victorian times
engineering mixed in
With modern engineering.
Narrator: It's the only
one of its kind in the world,
Combining modern
adrenaline sports with history.
White: We employed a team of
french fishermen who designed
The net system and then
the zip rope construction team
Were brought in to
install all of the anchors.
No machinery, pump,
crane, scaffolding was used.
Everything was done by hand.
Narrator: As the miners
before them, engineers worked
By hand, fixing anchors to
suspend giant net trampolines,
Slides, and tunnels.
White: The netting is
basically fishing nets.
The bounce actually comes
from the tension system
And the cables that actually
connect the main net floor
To the walls themselves.
Narrator: People come
from all over the world to play
On this enormous underground net adventure.
White: I just love the
way that we kind of mix
The modern technology with
The historical side of things.
♪
It's just truly unique and
pretty mind-blowing, really.
Narrator: Throughout it's history,
Men and even children risked their lives
To excavate these huge
caverns for this precious slate.
Now those underground realms
have been given a new life.
Man: [ laughs ]
Whoo!
♪
Narrator: Iceland, located
just outside of the arctic circle.
This land of fire and ice
embraces it's extremes.
While 11% of this island
is covered with glaciers,
Beneath the frozen surface
lies a molten volcanic heart.
What do we have here?
Wow.
Narrator: How do experts
preserve a pre-historic,
Subterranean monument...
You have to realize how much heat,
How much power is in here.
Narrator: ...And what can it reveal
About the origins of our planet?
Thordarson: This is
what constructed iceland.
It all came from here.
♪
Narrator: In a country
that is still being shaped
And formed by its mighty
volcanoes and powerful glaciers,
Just 25 miles from
iceland's capital, reykjavík,
Lies one of the country's most spectacular
Underground caverns.
Thor thordarson, a professor of geology,
Has been mesmerized by this area of iceland
For over 50 years.
Thordarson: The first
time I came here was 1965.
I came here with my parents.
First time I saw this, just simple "wow."
It was amazing.
Narrator: This sub-surface maze,
Known as raufarhólshellir,
is almost a mile in length.
In icelandic, the name
loosely translates to
"the cave on the hill with the holes."
Its a fantastic place for volcanology,
Absolutely fantastic, it has everything.
Narrator: The mysterious
tunnel is actually a lava tube,
A void left underneath a
hardened layer of volcanic rock
Once the molten material has drained away.
This is one of 500 lava
tubes known of in iceland
And is one of the most spectacular.
One of the things that has
always impressed me here
Is these beautiful skylights
Where you can actually see up into the sky.
Narrator: Raufarhólshellir
was formed in this lava field
More than 5,000 years ago.
Thordarson: Lava constructed the tunnel
And it just walked across
the landscape gradually.
As the lava came out of the narrow tunnel,
These are all what we call
lobes, and they broke out.
Narrator: With each volcanic eruption,
Surges of lava forced their way through
The cooling skin of rock,
one giant globule, or lobe,
Of lava after another.
As the tunnel grew longer and longer,
The lobes resembled a
series of successive domes.
Thordarson: The lava was
lengthened step by step,
Gradually moving forward,
but then at some point,
The pressure exceeds
the strength of the crust
And lava breaks through it.
And it breaks through
a fairly narrow point,
And then it spreads out.
And then you repeat this process.
Narrow point, spreads out.
So, the chambers represent the lobe.
The chute represents the point of breakout.
Narrator: As the active lava traveled,
It left behind its story
within the hard crust.
Thordarson: Earth's
history is written into rocks.
All we got to do is learn
how to read the rocks.
Narrator: While the river
of lava continued to flow
Inside the crusty shell,
A 33-foot-high ceiling solidified on top,
Creating a network of colossal
chambers up to 100 feet wide.
In all, there are 14 separate chambers
In this lava tunnel that have been created
By successive eruptions
over many millennia,
Leaving secrets behind
about this island and our planet.
As a geologist,
Thor's ultimate goal is to locate the point
From where these violent
volcanic eruptions began.
Thordarson: As you walk through it,
You realize you're walking back in time
In terms of lava and
placement because the ones
Which were furthest down when we started,
That's the last lobes that were formed.
As we go back this way,
We're getting into older and older parts
Of the lava flow field,
and what we're seeing
Is basically how the lava
was building this flow field
Step by step.
These are very important
constructive forces.
This kind of a system is
the reason why I study this.
This is what constructed iceland.
Narrator: Records show
that the first exploration
Took place here in 1909.
Since then, the whole system
became a source of inspiration
To a growing number of visitors.
Among them, halli kristinsson,
One of iceland's most famous mountaineers
And now an expert in extreme environments.
Kristinsson: When I
came here for the first time,
I had been to several caves
But this one was by far the biggest.
But I remember the first time coming here
And seeing skylights like this,
And not just one of them,
but like three of them,
And that's very, very unique.
Narrator: Over the course of a
century, the breathtaking beauty
Of the cave drew in curious tourists,
Inevitably causing serious
damage to the fragile terrain.
In 2016, the tunnel was
temporarily closed to the public
In order for halli and his team to save
This subterranean space.
So what does it take
for experts to preserve
A prehistoric treasure
for future generations?
Narrator: Raufarhólshellir
is the longest lava tube
In iceland and reveals a fascinating tale
Of the country's past.
But a century of
tourist travel took its toll
On the fragile environment
And this underground marvel
had to be temporarily closed
For preservation to save its
story for future generations.
It took us a while to figure out
What would be the best material to walk on,
Where we need to build platforms.
Raufarhólshellir gets as
close as possible being natural.
Also, everything we used, all the bolts,
They will not penetrate any
chemical into the environment.
So the idea was always that
we can go here in 30 years,
Take everything out, and the cave will be
Exactly like it was before.
Narrator: Creating access for visitors
That makes low impact
on this geologic marvel
Is crucial.
But the farther into the chambers you trek,
The less natural light
there is until eventually,
You can't see anything.
People don't realize how pitch black it is
Inside the lava cave because the light
Nor the sound travels anywhere.
So, just few meters further in here,
If we would turn off the light,
We would have 100% complete darkness.
And the eyes start to play trick on you.
You start to see white spots
on the corner of your eyes.
The eyes trying to find something.
If you are in here for
lets say, two months,
You develop cave blindness,
and you become blind.
You actually become blind.
Your eyes will adjust back
once you are out in the daylight,
But part of your eyesight
will get ruined forever.
Narrator: In order to truly appreciate
All this subterranean marvel has to offer,
Its wonders are enhanced by
a complex system of cave lights
Designed to work in harmony
With the natural prehistoric environment.
The goal was to bring to life the iron,
Phosphorous, potassium,
and other vibrant minerals
Deposited by awesome volcanic power.
We don't use colors in the lights.
We don't need that because
we have all the colors
In the world in the formations of the lava.
You have to use your imagination
to realize how much heat,
How much power is in here
That it's creating rock as it flows.
Its a flowing rock.
Narrator: And its caverns like these
That offer scientists a unique opportunity
To better understand
the origins of life on earth.
Kristinsson: There's no
moss or any life at all in here
Apart from bacteria.
We have here in the ceiling
this white sparkling thing
Which is a bacteria
that only grows in caves.
So its actually been
studied, for example, by nasa.
They study cave bacteria in iceland.
Narrator: And it's this unique environment
That motivates geologist thor thordarson
To continue exploring its depths,
Stepping further into this
cave than he's ever been before
To find the source from
which the lava has flowed
Over thousands of years.
Thordarson: This is a huge chamber.
This is the hole in the house.
Narrator: It's at least 65 feet wide,
And when it was active,
It must've been about 65 feet high.
A huge amount of lava
has gone through here.
The length of it is at least 330 feet.
Thordarson: We see along here
Different stages of lava
flowing through here,
So at some point, it
must've filled this chamber.
And then as the lava level dropped,
Then we can see those
different marks here on the walls.
For me, this is huge.
So this is a narrow bit of the lava tunnel.
Narrator: Thor has reached a place
That few people ever get to see.
Thordarson: Otherwise you see, right there.
What do we have here?
Wow.
Narrator: Nearly a mile
from the tunnel entrance...
The vent from which the
earth's molten core erupted
And created this entire
underground masterpiece.
This is absolutely spectacular.
It's a lava-fall.
The lava that actually
created the lava tunnel
Came out of here.
Its just like a river system,
Difference is, it's in the
underworld, it's actually
In a cave, it's enclosed,
we don't see it at the surface.
It all came from here.
Narrator: Raufarhólshellir
is a stunning demonstration
Of primordial power,
Super-heated molten rock
forcing through the crust
And solidifying to leave
behind caves of many colors.
An epic sight to be enjoyed
for centuries to come.
Thordarson: You are
in an underground world.
This is a world in its own right.
♪
A vast world of secret tunnels.
Oh, my goodness.
Why were they so important during
One of the world's bloodiest battles?
This is the biggest single
concentration of graffiti
On the somme.
Narrator: What unbelievable uses
Have been found for these welsh caverns...
Amazing just to think that everything
Was actually mined here by hand.
Narrator: ...Carved
out here by slate miners
In the harshest conditions.
They are razor sharp.
They would cut you in half.
Narrator: And deep beneath a glacier...
It's the most volcanically
active spot on earth.
Narrator: ...What stunning
spaces lead to an entrance
To earth's fierce and fiery core?
Wow!
Beneath our feet lie
extraordinary chambers, caves,
Vaults, and tunnels...
The span and the size is just crazy.
Narrator: ...Some designed
and built by humans,
Others formed over thousands of years.
But how were they created and adapted?
By whom?
And why?
You've got to face your fears.
Narrator: Throughout
history, subterranean life
Has captured our imagination.
We're going further and
deeper to unearth the mysteries,
The stories, and the secrets
of underground marvels.
France is the largest
country in western europe,
With its northern region
dotted by quaint farms
And small towns.
40 feet below this picturesque
village lies a complex
Of tunnels carved out
of the soft chalk bedrock.
These chambers have
protected generations of locals
And would play a key role
in one of the bloodiest battles
In human history.
The entire village would
disappear underground.
Narrator: How did the
tunnels play a crucial role
During the first world war...
It's one of those places
where time stands still.
Narrator: ...And how did they inspire those
Who sought refuge within them?
Lend some thought to him for middle earth.
♪
100 miles north of paris, bouzincourt
Is an isolated village
of around 500 people.
The church of saint honoré
dominates the surrounding
Countryside, and within it lies an entrance
To a secret world.
These tunnels contain mysteries
from many historical eras.
Battlefield expert vic piuk
has been researching these
Relics of the past.
Piuk: The first thing you
actually see here is, obviously,
A manmade structure of
bricks, but then you enter
Another world altogether.
Narrator: The villagers of bouzincourt
Started digging here in the
15th century to escape their
Harsh reality above ground.
They would've found the
porous, chalky terrain easy
To excavate by hand because it drains well
And requires no additional support.
The tunnels were built for two reasons.
They would come down
here for safety, for security,
Or to see out a particularly bad winter,
Because it's the same
temperature all year around.
It might be absolutely freezing up above,
But here it would be
actually more hospitable.
Construction started relatively shortly
After the hundred years'
war, when there had been lots
Of battles here coming
backwards and forwards.
Narrator: The hundred years'
war was a century-long series
Of battles fought between
France and England,
With the french ultimately
regaining their territory
From the british in 1453.
But there would be many more
wars in the coming centuries,
And these tunnels would
continue to give the villagers
A secret hideaway to take
refuge from the fighting.
Piuk: Incredibly, the entire
village would disappear
Underground, bringing with
them their cattle, their sheep,
Their pigs, and they
would hunker down here.
These were secret places.
As far as the enemy was concerned,
They'd find a deserted village.
The entrances would've been hidden.
Armies that passed
through this wouldn't have
The slightest idea.
Narrator: The villagers dug
out tunnels and 50 separate
Rooms to provide
accommodation for themselves
And their herds.
The largest of them covers 320 square feet.
The rooms were actually
used by individual families
In times of crisis.
There would've been a wooden door here,
Then you turned the lock on
it, 'cause it was your property.
You can actually see the wood is long gone.
You can still actually see evidence
Of where the door frame was.
This was the environment for the family.
They would've actually
lived in here and had their bits
And pieces here.
But actually, this was for the cattle.
And these were actually the
stalls for the pigs, the sheep,
Whatever beasts they
actually had down here.
Narrator: Vic is meeting local historian,
Jean luc ruvian, who has
traced his own family back
Through time by analyzing
the carvings on the tunnel walls.
[ speaks french ]
Okay. That was actually his grandfather
And his two great-uncles.
Piuk: Jean luc comes
from a long-standing family.
They've been here for centuries.
There's a long connection here.
Narrator: The most
telling carving can be found
At the entrance to one of
the underground chambers.
Right, this is the oldest inscription here
In the shelters.
Members of his family,
all those generations ago,
Slept in this cave.
This is unique.
In the year 1711, europe endured
One of the coldest winters
on record, and this graffiti is
A relic of the families who survived it.
Piuk: Almost, without a shadow
of a doubt, the entire family,
The entire village, came
down into these caves
To see out that awful period.
[ speaks french ]
He says it's a very important
place for the community
Here in bouzincourt because
it's a place that bears witness.
Narrator: Yet the tunnels
played their biggest role
In bouzincourt's history when
the tiny village found itself
On the front line during world war I.
It was a war between two power blocks,
One headed by britain and
France, the other by germany.
It lasted from 1914 to 1918.
Bouzincourt is close to
the site of one of the war's
Deadliest battles along the
course of the river somme.
Piuk: French troops are
actually in occupation here.
The somme, actually,
was a quiet period until
The battle of the somme in
1916 when the british arrived.
Narrator: The villagers
of bouzincourt fled,
Leaving the british army
to protect the western front.
And some would leave their mark
In these underground tunnels forever.
This is the biggest single concentration.
This is remarkable.
♪
♪
Narrator: During the
atrocious battle of the somme,
Soldiers fighting in muddy,
disease-infested trenches
Found these secret tunnels
hidden underneath bouzincourt,
France, as a welcome refuge,
like generations before them.
So to be 12 meters underground
in structures such as this,
Was heaven-sent for the british military.
Immediately what you see
here, it's the life of the man
Actually lived when they were down here.
Soldiers did everything down here.
Seems that this could
actually have been the chapel.
There at the back, the
earthenware jar is actually used
For rum ration.
Soldiers actually got a daily tot of rum
And it would've been very
welcome to keep out the cold.
Narrator: The battle of the
somme lasted five months
From July to November 1916.
On the first day, more
than 19,000 british soldiers
Were killed by shelling
and machine gun fire,
The largest loss of life ever
suffered by the british army
In a single day.
The tunnels provided those
brave young men with shelter
And relief from the
carnage of the western front,
As nearly three times more soldiers
Crammed into these caves
Than actual inhabitants of bouzincourt.
They left behind small
signs of their humanity
On the soft walls of their refuge.
We just see the names and
the marks they left in history.
These were real people.
These men all mattered to
their wives and loved ones.
And you could lose sight of
that, but you don't when you're
In a place like this because
you can see their names.
This is the biggest single
concentration of graffiti
On the somme.
This is remarkable.
A veteran of the great war
Said it was 90% sheer
boredom, 10% sheer terror.
These men could be here
today and gone tomorrow.
This was maybe a final chance
To leave your mark for posterity.
Narrator: There are more
than 1,500 signatures
And drawings in these tunnels that date
From the first world war.
Some, celebrities of their
time, and some who would go on
To leave a lasting impact on society.
Among the names, american
and canadian soldiers
Billeted here as part of the allied force.
There's actually two brothers
see, side by side here.
Look, can see this e.A. Jarrett
and s.H.R. Jarrett, canadians.
Narrator: Where soldiers have given their
Regimental numbers,
historians have been able to trace
Their military careers, both
during and after the war.
Ray klinsing. This guy
was from north dakota.
He won two military medals for bravery.
He survived the battle of the somme.
He actually died in 1981.
Narrator: Another carving refers to a
Particular british regiment.
One of its officers was
a celebrity at the time.
Lovely regimental badge
here of the 17th middlesex,
The die-hards was their nickname.
They were the unit that
had a certain walter tull,
Who was a pre-war
footballer for tottenham hotspur
And northampton town.
He was one of the first black
professionals in footballers,
And certainly the first
black british officer.
He was actually to die
not far from here in 1918.
Narrator: 3 million soldiers fought in the
Battle of the somme above
these very caves, and 1 million
Were wounded or killed,
making it one of the bloodiest
Battles in human history.
During one of many bombardments,
The church of saint honoré was destroyed.
It was rebuilt in 1920 in
the shape of an artillery shell
As a tribute to the fallen.
Richard stenning
recently discovered that his
Great-grandfather,
major-general william rycroft,
Was among the british
forces here over 100 years ago.
It's intriguing to come here and retrace
Some of his steps.
Narrator: Richard's here
to explore the tunnels
Where his great-grandfather
once took shelter.
♪
As a major-general,
Richard's great-grandfather,
william, would've commanded
A division of around 18,000 to 20,000 men.
There were 50 british divisions
at the battle of the somme
During this epic struggle
on the western front.
Unlike in later conflicts,
during world war I,
Senior officers still found
themselves in mortal danger
On the front line, and
william rycroft diligently noted
The trials that faced the allied forces.
That was the original, was it? Yeah.
William rycroft's account of the first day
Of the battle shows the risks that he took,
Along with his men while
around them, vast numbers
Of british and allied lives were lost.
Being the officer commanding,
you've got these lives
Of tens of thousands of
men as your responsibility.
How would I have coped with that?
Could I have stood in
his position and done that?
It makes it all real.
♪
The war devastated an entire generation,
Yet some may have found inspiration.
Also present at the battle of the somme was
A 24-year-old officer
who would go on to make
A lasting impression on the world.
There's some anecdotal
evidence that j.R.R. Tolkien
Was actually here. I saw something.
Yeah, that he served around here.
Yeah, he said he served here,
That's not open to debate.
The famous "lord of the rings" author,
J.R.R. Tolkien, undoubtedly
drew on his wartime experiences
In his epic saga of good versus evil.
Underground worlds play a
crucial role in the fantasy land
He created, named middle earth,
From the hobbit holes to the mines of moria
And the dwarven realms.
He could have very well
been in these tunnels.
It would've been very cool
to have him left his mark here.
That would've been something, yes.
Lend some thought to
him for middle earth, right?
Major operations at the battle of the somme
Ended on November 18th, 1916.
The walls serve as a lasting
memory to allied soldiers
Who stood firm in the fight
against military aggression.
These caves have offered
sanctuary for centuries,
And perhaps will continue
to do so for years to come.
♪
As part of the united kingdom,
wales is a small country
Of 7,700 square miles,
dense with natural woodlands,
Quarries, and agriculture,
and a hard-working population
Of 3 million people.
Beneath these peaks lie
natural resources formed
Over millions of years and
carved out by generations
Of workers, including young children.
What these people went
through every day just to
Put some food on the table.
Narrator: What conditions
did the workforce endure
As they mined the earth's riches?
When these pieces go, they are razor-sharp.
They would cut you in half.
Narrator: And now that its
era of heavy industrial mining
Is over, what new underground
marvel is making use
Of the subterranean spaces left behind?
Man: Whoo!
♪
Narrator: The hills surrounding the town
Of blaenau ffestiniog are
strewn with centuries of rocky
Waste material left over
from mining that defined this
Local community for generations.
Best known for its use in
roofing and flooring, slate was
First mined here by the
romans around the year 45 a.D.
But it wasn't until the
industrial revolution in the
Mid-19th century that it became
a sought-after commodity.
And for the men who extracted
it, it would be a harrowing
Place to work, with dangers
lurking around every corner.
♪
The llechwedd slate mine in wales
Extends two thirds of a mile
Under the mountainside and
contains more than 15 miles
Of tunnels and 250 chambers
spread over 16 levels.
They're accessed by a narrow gage railway,
The steepest of its kind in the u.K.
Brian jones once worked in the mine
On the maintenance
team, and is now a guide.
The world-famous slate vein was formed
500 million years ago
when this area of wales was
Beneath a prehistoric ocean.
A massive volcanic eruption
put huge amounts of heat
And pressure on the seabed,
pushing it up to an angle
Of 33 degrees and baking
it solid in the process.
During the slate mining boom of the 1880s,
The population of blaenau ffestiniog
Rose from around 3,400 to more than 11,000.
Llechwedd was one of
several mines in the town,
And miners flooded in
to work this rich seam.
Now, this looks to me
like good-quality slate.
Look at the very fine
graining in the slate itself.
Can see here where there's
been a previous miner drilling,
And you can see the blackness
in here where the gunpowder,
Where the blast has been.
Narrator: By candlelight,
men would use basic hand tools
Called jumpers to work
their way into the rock
Before setting an explosive charge
To blow away large pieces.
Brian: That's a natural crack in the rock.
A rock man would drill in here.
This depth, charge it, and blow it down.
When he blows this out,
this nice lump of slate would
Fall down here.
Up to about 1818, 1819,
this would've been done
By a jumper manually.
Narrator: By the end of the 19th century,
During the industry's peak
due to a boom in victorian
House building, half a
million tons of top-quality slate
Was extracted every year.
This was enough to produce
tiles to cover an estimated
150 million square feet of roof.
Local phil jones traces his
family connection to this mine
Back three generations.
I remember coming here
with my father and my mother.
My father always used
to say over there is where
He worked with his father,
my grandfather, in the '70s.
Narrator: Today, phil
shares the tough world
Of his ancestors with visitors to the cave.
This is where my father
and my grandfather worked.
My father was my grandfather's apprentice,
But rock men was what they were.
They would be extracting the slate.
Narrator: In 1912, drills
using compressed air
Were introduced to replace
the primitive hand tools.
Even though modern tools were brought in
To excavate slate more
efficiently, they continued
To use more familiar
methods to suspend themselves
High up on the rock face
to reach the valuable slate.
It was a death-defying maneuver.
The miners would scale
the wall using metal chains.
The reason why they used
chains was 'cause rope would
Actually rot in these
conditions eventually.
So that locks into position
and it frees my hands,
Then I can work on the rock surface.
Just move my leg like that,
and I'm out of a situation fast.
The men, they had to pay for the material
In the early days, and
what they would do is they'd
Fasten the chains to
pegs like this with fuse wire
And then they'd light the
fuse right here and they could
Get the chains back.
So they looked after
their tools and later on,
When the company paid
for the tools, they just left
These chains in place.
Don't think I could do that job.
Narrator: This subterranean
space has always attracted
Adventurers, now as it did then.
It would take a large team up to 20 years
To excavate a chamber of this size.
There's about 10 chains here.
Now, there would've been a
man on each of these chains,
So this rock face would've
been quite a busy rock face.
They would've been up
there for maybe 10 hours.
Narrator: It was a loud and
hazardous place to work.
Life expectancy of a
miner was only 45 years.
Now, you could be working
down in this chamber here,
Looking up at these
dangerous pieces here hanging
Over your head all day.
When these pieces go, they are razor sharp.
They would cut you in half.
So many men were killed down here.
♪
Narrator: After the
miners had left for the day,
Workers known as danger
men had the perilous job
Of coming in at night to
remove unstable rocks.
Brian: They would've been
working on the tops of these ladders.
Wrap your leg around the top rung,
Hang on for dear life.
Crowbar in one hand, lantern in the other.
Levering and banging
away at these pieces here,
Getting these dangerous
pieces down from here,
Making this place safer for the next day.
Now, they weren't paid
much for this job, even though
They risked their lives every day.
A lot of respect from the
men, and a lot of respect
From the management for doing this.
It's important that everybody
remembers the people that
Came here, the conditions
they worked under.
It must've been traumatic
for these young boys
Of 18 years old working down
here in the cold and the damp.
Narrator: The children,
as young as 5 years old,
Served in the mines by
chipping, washing, and sorting.
It was one of the worst
places to work if you were a kid
In the early to mid 1800s.
The mines were cramped, poorly ventilated,
And highly dangerous.
Children were in danger of
being killed from explosions,
Roof falls, or being run over by carts.
Brian: These places should be kept open
As long as possible.
The people can reflect
when they come down here.
♪
♪
Narrator: On the other
hand, the safest and most
Lucrative job at the mine
happened above ground.
Richard roberts began
working in the slate mine industry
When he was just 15 years old in 1945.
His job was to create tiles,
Which involved more skilled labor.
There you go.
Now it's the ideal size of a roofing slate.
This is where they made the wages.
These men up here actually made money.
The men underground didn't as such.
Narrator: When slate mining began here,
It produced 90% waste,
which can be seen strewn
All over the hillsides in north wales.
But with better machinery
in working mines today,
Waste is only 10%.
There you go.
The finished slate would find its way
To the docks in liverpool
before being shipped
All over the world.
The mine finally closed
down in the early 1970s
As competition from
overseas imports increased,
Making way for a modern-day transformation.
After lying dormant for
several years, developers saw
The potential for a
whole new lease on life.
When part of the mine
was reopened for tourism,
Visitors were able to
follow in the footsteps
Of the men who shaped this countryside.
And in recent years, these
worlds that once spelled danger
Have been transformed for
some rather unexpected use,
Including the creation
of an unlikely delicacy.
Narrator: The unique environment
of the slate caverns in wales
Is the ideal place for
an unexpected delicacy.
In an area of the mine
not open to the public,
An award-winning cheese is now produced.
When it's at 11 month old
and it's stacked on the shelves
Here for three months, and
then carried back upstairs
To creameries to be cut and sold.
Narrator: As a quality manager
for south caernarfon creameries,
Shon jones is keenly aware of how difficult
It is to find the right place
to store 50 tons of product.
Shon: Bringing the cheese
down here where the atmosphere
And temperature and the
pressure down here gives it
A unique, intense flavor to it.
Narrator: 500 feet below
the surface, a cavern originally
Excavated in 1856 for creating
rooftops is now packed full.
Shon: If the temperature was
too low, then the cheese wouldn't
Move on, they wouldn't mature,
Go through the maturing process.
So this is extra mature
cheddar now ready to go back
To the creamery, so what I'll be doing now
Is checking this cheese
for the flavor and the profile
Before we take it back.
This stuff's good to go.
Narrator: Each day, a
ton of cheese is brought up
And down on the vertical
train originally used
For hauling slate.
Yet an even more surprising
new use of this subterranean
Space can be found elsewhere
in the caves, inspired by
The harrowing work of the miners who hung
From the ceilings years ago.
Carwyn: The first time I came
down, I was just blown away
By the sheer size of the chambers.
Just to think that everything
was actually mined here by hand
And taken out by hand is just amazing.
Narrator: In 2014, the
world's first underground
Trampoline park opened inside the caverns.
It's a shocking transformation
from the dangerous world
In which children once labored side by side
With their fathers.
It's like victorian times
engineering mixed in
With modern engineering.
Narrator: It's the only
one of its kind in the world,
Combining modern
adrenaline sports with history.
White: We employed a team of
french fishermen who designed
The net system and then
the zip rope construction team
Were brought in to
install all of the anchors.
No machinery, pump,
crane, scaffolding was used.
Everything was done by hand.
Narrator: As the miners
before them, engineers worked
By hand, fixing anchors to
suspend giant net trampolines,
Slides, and tunnels.
White: The netting is
basically fishing nets.
The bounce actually comes
from the tension system
And the cables that actually
connect the main net floor
To the walls themselves.
Narrator: People come
from all over the world to play
On this enormous underground net adventure.
White: I just love the
way that we kind of mix
The modern technology with
The historical side of things.
♪
It's just truly unique and
pretty mind-blowing, really.
Narrator: Throughout it's history,
Men and even children risked their lives
To excavate these huge
caverns for this precious slate.
Now those underground realms
have been given a new life.
Man: [ laughs ]
Whoo!
♪
Narrator: Iceland, located
just outside of the arctic circle.
This land of fire and ice
embraces it's extremes.
While 11% of this island
is covered with glaciers,
Beneath the frozen surface
lies a molten volcanic heart.
What do we have here?
Wow.
Narrator: How do experts
preserve a pre-historic,
Subterranean monument...
You have to realize how much heat,
How much power is in here.
Narrator: ...And what can it reveal
About the origins of our planet?
Thordarson: This is
what constructed iceland.
It all came from here.
♪
Narrator: In a country
that is still being shaped
And formed by its mighty
volcanoes and powerful glaciers,
Just 25 miles from
iceland's capital, reykjavík,
Lies one of the country's most spectacular
Underground caverns.
Thor thordarson, a professor of geology,
Has been mesmerized by this area of iceland
For over 50 years.
Thordarson: The first
time I came here was 1965.
I came here with my parents.
First time I saw this, just simple "wow."
It was amazing.
Narrator: This sub-surface maze,
Known as raufarhólshellir,
is almost a mile in length.
In icelandic, the name
loosely translates to
"the cave on the hill with the holes."
Its a fantastic place for volcanology,
Absolutely fantastic, it has everything.
Narrator: The mysterious
tunnel is actually a lava tube,
A void left underneath a
hardened layer of volcanic rock
Once the molten material has drained away.
This is one of 500 lava
tubes known of in iceland
And is one of the most spectacular.
One of the things that has
always impressed me here
Is these beautiful skylights
Where you can actually see up into the sky.
Narrator: Raufarhólshellir
was formed in this lava field
More than 5,000 years ago.
Thordarson: Lava constructed the tunnel
And it just walked across
the landscape gradually.
As the lava came out of the narrow tunnel,
These are all what we call
lobes, and they broke out.
Narrator: With each volcanic eruption,
Surges of lava forced their way through
The cooling skin of rock,
one giant globule, or lobe,
Of lava after another.
As the tunnel grew longer and longer,
The lobes resembled a
series of successive domes.
Thordarson: The lava was
lengthened step by step,
Gradually moving forward,
but then at some point,
The pressure exceeds
the strength of the crust
And lava breaks through it.
And it breaks through
a fairly narrow point,
And then it spreads out.
And then you repeat this process.
Narrow point, spreads out.
So, the chambers represent the lobe.
The chute represents the point of breakout.
Narrator: As the active lava traveled,
It left behind its story
within the hard crust.
Thordarson: Earth's
history is written into rocks.
All we got to do is learn
how to read the rocks.
Narrator: While the river
of lava continued to flow
Inside the crusty shell,
A 33-foot-high ceiling solidified on top,
Creating a network of colossal
chambers up to 100 feet wide.
In all, there are 14 separate chambers
In this lava tunnel that have been created
By successive eruptions
over many millennia,
Leaving secrets behind
about this island and our planet.
As a geologist,
Thor's ultimate goal is to locate the point
From where these violent
volcanic eruptions began.
Thordarson: As you walk through it,
You realize you're walking back in time
In terms of lava and
placement because the ones
Which were furthest down when we started,
That's the last lobes that were formed.
As we go back this way,
We're getting into older and older parts
Of the lava flow field,
and what we're seeing
Is basically how the lava
was building this flow field
Step by step.
These are very important
constructive forces.
This kind of a system is
the reason why I study this.
This is what constructed iceland.
Narrator: Records show
that the first exploration
Took place here in 1909.
Since then, the whole system
became a source of inspiration
To a growing number of visitors.
Among them, halli kristinsson,
One of iceland's most famous mountaineers
And now an expert in extreme environments.
Kristinsson: When I
came here for the first time,
I had been to several caves
But this one was by far the biggest.
But I remember the first time coming here
And seeing skylights like this,
And not just one of them,
but like three of them,
And that's very, very unique.
Narrator: Over the course of a
century, the breathtaking beauty
Of the cave drew in curious tourists,
Inevitably causing serious
damage to the fragile terrain.
In 2016, the tunnel was
temporarily closed to the public
In order for halli and his team to save
This subterranean space.
So what does it take
for experts to preserve
A prehistoric treasure
for future generations?
Narrator: Raufarhólshellir
is the longest lava tube
In iceland and reveals a fascinating tale
Of the country's past.
But a century of
tourist travel took its toll
On the fragile environment
And this underground marvel
had to be temporarily closed
For preservation to save its
story for future generations.
It took us a while to figure out
What would be the best material to walk on,
Where we need to build platforms.
Raufarhólshellir gets as
close as possible being natural.
Also, everything we used, all the bolts,
They will not penetrate any
chemical into the environment.
So the idea was always that
we can go here in 30 years,
Take everything out, and the cave will be
Exactly like it was before.
Narrator: Creating access for visitors
That makes low impact
on this geologic marvel
Is crucial.
But the farther into the chambers you trek,
The less natural light
there is until eventually,
You can't see anything.
People don't realize how pitch black it is
Inside the lava cave because the light
Nor the sound travels anywhere.
So, just few meters further in here,
If we would turn off the light,
We would have 100% complete darkness.
And the eyes start to play trick on you.
You start to see white spots
on the corner of your eyes.
The eyes trying to find something.
If you are in here for
lets say, two months,
You develop cave blindness,
and you become blind.
You actually become blind.
Your eyes will adjust back
once you are out in the daylight,
But part of your eyesight
will get ruined forever.
Narrator: In order to truly appreciate
All this subterranean marvel has to offer,
Its wonders are enhanced by
a complex system of cave lights
Designed to work in harmony
With the natural prehistoric environment.
The goal was to bring to life the iron,
Phosphorous, potassium,
and other vibrant minerals
Deposited by awesome volcanic power.
We don't use colors in the lights.
We don't need that because
we have all the colors
In the world in the formations of the lava.
You have to use your imagination
to realize how much heat,
How much power is in here
That it's creating rock as it flows.
Its a flowing rock.
Narrator: And its caverns like these
That offer scientists a unique opportunity
To better understand
the origins of life on earth.
Kristinsson: There's no
moss or any life at all in here
Apart from bacteria.
We have here in the ceiling
this white sparkling thing
Which is a bacteria
that only grows in caves.
So its actually been
studied, for example, by nasa.
They study cave bacteria in iceland.
Narrator: And it's this unique environment
That motivates geologist thor thordarson
To continue exploring its depths,
Stepping further into this
cave than he's ever been before
To find the source from
which the lava has flowed
Over thousands of years.
Thordarson: This is a huge chamber.
This is the hole in the house.
Narrator: It's at least 65 feet wide,
And when it was active,
It must've been about 65 feet high.
A huge amount of lava
has gone through here.
The length of it is at least 330 feet.
Thordarson: We see along here
Different stages of lava
flowing through here,
So at some point, it
must've filled this chamber.
And then as the lava level dropped,
Then we can see those
different marks here on the walls.
For me, this is huge.
So this is a narrow bit of the lava tunnel.
Narrator: Thor has reached a place
That few people ever get to see.
Thordarson: Otherwise you see, right there.
What do we have here?
Wow.
Narrator: Nearly a mile
from the tunnel entrance...
The vent from which the
earth's molten core erupted
And created this entire
underground masterpiece.
This is absolutely spectacular.
It's a lava-fall.
The lava that actually
created the lava tunnel
Came out of here.
Its just like a river system,
Difference is, it's in the
underworld, it's actually
In a cave, it's enclosed,
we don't see it at the surface.
It all came from here.
Narrator: Raufarhólshellir
is a stunning demonstration
Of primordial power,
Super-heated molten rock
forcing through the crust
And solidifying to leave
behind caves of many colors.
An epic sight to be enjoyed
for centuries to come.
Thordarson: You are
in an underground world.
This is a world in its own right.
♪