Underground Marvels (2019–…): Season 1, Episode 8 - The Maginot Line - full transcript

Narrator: A 2,000-year-old city

That was forced to dig deep to survive.

This whole place was
covered up by dirt and water.

Narrator: What subterranean
secrets are being revealed?

It was crazy finding
something totally unexpected.

Narrator: A vast, nationwide network

Of subterranean fortresses...

...Designed to stop a nazi invasion.

And deep beneath a mountain,

A new discovery after 150 years.

Worley: Wow.



This is like a geologist's toy shop,

And I got all the toys.

Narrator: 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.

Istanbul, turkey, a transcontinental city

Straddling the bosphorous strait,

Where europe and asia meet.

For more than two
millennia, its location has been

Strategically important
to the ancient greeks

And then later the roman
and ottoman empires.

And underneath this cultural hub

Lie vast, mysterious worlds.

What extraordinary feats
of underground engineering

Allowed this city to thrive
for nearly 2,000 years?

Tuten: I'm looking at it like,

"wow, what made them do this?"

We're sitting on top of history.

And what subterranean secrets
are still being uncovered today?

It was crazy finding
something totally unexpected.

In the early 4th century,

Istanbul, then known as constantinople,

Was the newly formed
capital of the byzantine empire.

The site was a former ancient greek city,

Chosen by emperor constantine
as the new seat of government

Because of its central
location within the giant empire.

He named this city constantinople,

The city of constantine.

Over time, skilled artisans and builders

Created beautiful statues and sculptures,

But not all of their work

Is visible to the casual tourist today.

What they don't see are
these... giant, cavernous rooms

With elaborate detailing, called cisterns.

What were these massive
structures used for,

Religious worship,
burial or something else?

A clue lies within the
location of the city itself.

Even though it served as a major trade hub

Between europe and
asia, it had one crucial flaw.

Professor ferudun
ozgumus is an archeologist

And byzantine expert,

Who has been investigating
the oldest cistern ever discovered.

It's called theodosius cistern.

♪

Theodosius cistern was discovered

Under a 20th-century mansion,

Neighboring a municipal building.

It is 150 by 82 feet

And has 32 marble columns 30 feet tall.

So how were these robust
subterranean structures

Built and why?

The walls of the cisterns give clues

As to what they were built for.

They were typically made
from brick, 13 feet thick.

Builders then needed to guarantee

They would be watertight

Because despite the booming society,

Constantinople lacked one of
the most necessary elements

To maintain life... Fresh water.

With people flocking here
from all over europe and asia,

An ingenious solution was needed.

In the 6th century a.D.,

During the reign of the beloved emperor,

Justinian, water was transported 12 miles

By a series of aqueducts
from the belgrad forest

And stored in the city's
center in underground tanks.

The 8-year renovation of theodosius

Has been true to the
cistern's original design.

Across the ceiling are
holes leading to the surface

Through which water
was available to everyone.

The people of constantinople had perfected

The design and construction of cisterns.

There are remarkable similarities

Between all of them.

What is clear from the design
and construction of these

1,700-year-old structures
is that they were built to last,

Even through natural disasters.

Over the centuries,

As the ancient city has been redeveloped,

A staggering number of these
ancient subterranean rooms

Have been discovered.

Reportedly, 200 in total.

At least that's how
many they've found so far.

The most famous cistern
known to have survived

Beneath istanbul is basilica cistern.

Dr. Kerim altug is an
archeologist and historian

And has been researching
istanbul's cisterns

For more than 20 years.

This vast cavern,
measuring 1,500 by 700 feet,

Could be filled with 528
million gallons of water.

Its ceiling is supported
by 336 marble columns,

Each measuring 30 feet high.

The decoration on this
column resembles others

Found elsewhere in the city.

Ancient writings suggest
that the tier-like decoration

Pays tribute to the hundreds of slaves

Who died during the
construction of the basilica cistern.

Other columns were
recycled from previous relics.

In the northwest corner,
there are two striking columns

Standing on heads of medusa.

It's not known where these came from,

But the significance of their
use and orientation is clear.

In a newly christianized
city, mythological characters

Like these from the previous belief systems

Would have been demolished.

A local tradition also suggests

That the faces were positioned
sideways and upside down

To eliminate the terrifying
power of medusa's stare.

♪

Modern-day discoveries are
still being made in the ancient city

And one turkish store owner
got more than he bargained for

When he found that his shop

Sits on top of a historic byzantine site.

Tuten: I'm looking at it like,

"wow, we're sitting on top of history."

Narrator: The ancient city
of istanbul has revealed

Over 200 subterranean
caverns known as cisterns

And more are being discovered to this day.

When redeveloping an old
site for his latest shop in 2004,

Cenk tuten was in for a big surprise.

Tuten: There were three houses,

Double floors above.

The excavator hit

And that was one of the doors
that led us under those houses.

Thanks to the excavator, that's
how the whole thing started.

Narrator: Cenk's builders

Had uncovered a subterranean secret.

Tuten: This whole place was
covered up with dirt and water

And a bit of everything.

It was crazy finding
something totally unexpected.

Narrator: What they'd
found was an ancient cistern

Around 1,700 years old.

Cenk's carpet shop is on the site

Of an ancient royal palace.

This was the water for the upper class.

They were using it to shower.

They were using it to cook their meal

They were using it to drink it.

Narrator: This cistern
and its 18 marble columns

Would have provided water to
the great palace of constantinople

During the reign of emperor
justinian in the 6th century.

Can you imagine the water
that was preserved in here

Was actually drank by the royal families?

Narrator: He has invited dr. Kerim altug

To his carpet shop's
restored underground world

To learn more about its ancient purpose.

Okay, brick. Okay.

Okay. Alright.

Okay, fantastic.

Cisterns are no longer needed
for water supply in istanbul,

But experts and locals agree

They need to be maintained
for generations to come.

This had to be preserved
and had to be refurbished.

We're trying to provide
people the information

And the history that
they're actually stepping on.

Narrator: Cenk and his
colleagues have taken

Extraordinary steps to ensure

That nakkas cistern is preserved.

In order to protect and presume

The whole beautiful
history under this building,

We have a huge steel construction

That carries the weight
of the main building

And this way doesn't give
any pressure to the cistern itself.

Narrator: Many of istanbul's
subterranean cisterns

Have been transformed,

Giving them relevance
to life in the 21st century.

Ozgumus: Most of these
things are privately owned.

One of them is a
restaurant or beautiful hotel.

Some of them are museums

And some like this is exhibition hall.

We've had painters from
around the world coming.

We had musicians.

Ozgumus: There are a lot of things

To be discovered in istanbul.

Most of these buildings
in istanbul have mysteries.

Tuten: We're sitting on top of history.

If we drilled at the moment
on these roads over here,

We'd probably find more cisterns.

Dr. Altug: There is no other roman city

To compare with this size

And number of the water
storage units as constantinople.

♪

Narrator: France... a country shattered

By many of world war I's bloodiest battles.

When the war ended, the
french became obsessed

With preparing for future conflicts.

During the 1920s and '30s,

As germany rearmed and
world war ii was looming,

The french government decided to build

The largest network of
subterranean fortresses

The world had ever seen.

David: Hackenberg is called the monster,

It's the biggest fort.

It's huge.

Narrator: What 1930s
cutting-edge military technology

Lay in wait for enemy invaders

And why did it ultimately fail?

It could move the turret 360 degrees

And stop it at the exact
location they needed to.

Narrator: And what else is still
hidden from view to this day?

David: This part is secret.

♪

♪

Narrator: In 1929 andre maginot,

A world war I veteran
turned french minister for war,

Convinced his government

To build a defensive line
of 142 subterranean forts,

352 gun encasements,

78 shelters, 17 observatories,

And 5,000 fortified concrete bunkers

Along its entire eastern border,

As world war ii was looming.

♪

Its construction began in 1930

And was largely completed by 1939,

At a cost of $1.5 billion
u.S. In modern times.

This state-of-the-art,
massive military marvel

Was designed to deter and slow
down any direct german invasion

Across its border with France,

As well as serving as a morale boost

For the french soldiers who
suffered devastating losses

During world war I.

Underground defenses
avoided surprise attacks

On the french territory

And protected the borders
close to the industrial areas.

This defensive boundary
became known as the maginot line.

The largest subterranean fortress

Along France's 280-mile border with germany

Is at its northern-most point,

It's called hackenberg fort.

♪

Hackenberg is 12 miles
from the french/german border

At the highest point in the region.

Elise david is an expert
on hackenberg's history.

Hackenberg is called the
monster of the maginot line

Because it's the biggest
fault of all the line.

It was one of the first to be built,

So they put a lot of
effort and money into it.

It's more than 80 years old and still here.

It's huge.

Narrator: It took 1,800 people

Six years to build hackenberg fort

Between 1929 and 1935.

This vast 6-mile complex of tunnels,

Up to 300 feet belowground,

Was built to house 42
officers and 1,040 soldiers.

From this vantage point,

They could have two observatories

At the top of the hill

And combat blocks with
mortars and machine guns.

There are two main entrances,

One for ammunition, the other for soldiers.

It's so large that it has its
own train network and stations.

David: The trains were
used to carry all the tools,

Water, foods, all the
supplies for the soldiers,

And they used these trains only inside.

It works with electricity.

You have the trolley here
with the catenary on the roof,

And we still use it.

Narrator: The catenary is still
used to power the train system

Just as it did during the war,

But while the train system was
formerly used to move supplies,

Today the wagons transport
tourists visiting the fort.

Around 1,000 feet from the
munitions entrance to hackenberg

Is the main ammunition
storage area known as m1.

Nearly 400 tons of weapons
and artillery was kept here

Before being distributed
to the 17 combat blocks

Further inside the underground fortress.

So now you are inside the
gallery of the ammunition store

And one that was used by the soldiers

To stock all the ammunitions
in the different cells.

And one was the biggest inside this fort

And even inside the whole maginot line.

It's really huge actually.

You can almost get lost.

Narrator: The m1 ammunition
store was built in a "u" shape.

Of the 75,500 total shells
stored at hackenberg,

More than 34,000 were
here in the m1 magazine,

As well as all the light
ammunition for infantry.

M1 held 10 days' worth of munitions.

On one side of the "u," empty trains

Would wait to be loaded by soldiers.

And on the other side, fully
loaded trains with ammunition

Would be wheeled out of the exit.

Moving ammunition inside
m1 could only be done by hand.

Using the catenary train
system would have risked

The electricity sparking an explosion.

The soldiers moved the
wagons using a system

With a winch and chains.

Once inside the storage area,

Soldiers used a specially designed

Ammunition transportation system.

David: This is the monorail system.

Narrator: Overhead monorail
tracks allowed soldiers to lift

Heavy ammunition from the
storage area onto the wagons.

David: It still works.

Yes, it works.

These are the originals.

The same chains, the same monorail stand.

Narrator: Filled with explosives,

The m1 was built to keep
soldiers as safe as possible.

David: Here you have three
cells only for the gunpowder.

They had fire alarms inside here.

They had big tanks filled with water.

And so when the alarm rang,

The tanks that were use directly,

It was an automatic
system to shower all the cells

To flood this area in case on fire.

Narrator: The entrance and exit to the m1

Were also built with safety in mind.

They're curved,

So if anything exploded
inside the ammunition store,

The blast would be
directed out of hackenberg

Rather than in towards
the rest of the complex.

Elise is on her way to combat
block nine in the western wing,

More than half a mile
away from the m1 storage.

Secured within block
nine are the firing rooms

Reachable by 143 steps,
and at the top of the tower

Is one of hackenberg's
biggest innovations...

Another subterranean feat of engineering.

Narrator: The hackenberg
subterranean fortress

Near France's border with germany

Is a marvel of pre-world war ii ingenuity.

Within a large counterweight system

Operates a 163-ton
retractable artillery tower.

It houses two 5.3-inch howitzer cannons.

When the germans attacked,
each of the two soldiers

Could fire 6 rounds per
minute at a range of 3.7 miles.

Despite being high tech for its time,

It did have downfalls.

David: The soldiers were shooting blind.

They were waiting for the orders
from the command post downstairs

And thanks to the two observatory blocks,

They had all their coordinates.

They could move the turrets to 360 degrees

And stop it at the exact
location they needed to.

They had to believe
and trust the coordinates.

They were here just to fire.

[ whirring ]

The soldiers didn't have
any protection for their ears.

After a while, they used what they had...

Papers, tissues, anything.

For the two soldiers who
were inside the turrets,

It's like inside a bell.

So they had the vibration, the sound,

The smoke when they're fired,

So it would have been really difficult.

Narrator: Hackenberg
was the first and largest

Of France's subterranean fortifications.

Its construction informed how
many other underground forts

Were built and lived in

As part of the series
of protective fortresses

Spread along the french
border called the maginot line.

60 miles to hackenberg's east

Is France's second most powerful fort...

Simserhof.

Simserhof is located 2
1/2 miles west of bitshe

In the northeast of France
facing the german border.

It's built 100 feet below the surface

And like hackenberg,
has separate ammunition

And personnel entrances.

It has its own power utility plant

And main ammunition store

With a capacity of 33,600 artillery shells

That served eight combat blocks.

Simserhof took 9 years
to build, completed in 1939.

On August 21st of that year,

The entire maginot line
including simserhof fort

Was brought to a state
of readiness for war.

876 soldiers were now hidden underground.

Betty bruhl is an expert on simserhof

And how military personnel
lived in this subterranean fortress

While waiting for the germans to invade.

If soldiers were asleep in
the dark depths of simserhof

And the germans attacked,

They could be certain of finding their way

To the combat blocks quickly and easily.

In comparison to the horrific
trenches of world war I,

Living conditions for
soldiers in forts like simserhof

Were significantly better.

Here they even had a lounge,

Which was designed to
be a refuge for soldiers.

Soldiers living in simserhof
spent much of their time

Waiting for a nazi invasion.

They brought many elements
of their lives above ground

Into the subterranean fortress.

Finally, on may 10, 1940,

The germans launched their
blitzkrieg against the west.

Simserhof and the maginot
line initially remained calm,

But deadly exchanges were inevitable.

From June 21, 1940,
simserhof fired 13,500 shells

In just four days

As it defended itself and
surrounding fortifications.

Despite the strength and elaborate design

Of the maginot line fortifications,

They ultimately failed
to protect the country.

With german troops entering France

Via belgium in the north

As hitler's army bypass them entirely.

However, the immense
firepower and impenetrable design

Of these major subterranean fortresses

Meant the germans didn't
capture a single one of them.

The french eventually
surrendered to germany

On June 25, 1940.

It wasn't until June 30th,
and only when directly ordered

By commander in chief of the french forces,

That simserhof finally relinquished control

To the germans.

The underground
fortresses that continue to line

These borders are a
constant reminder of the threat

France faced during world war ii.

Beneath the idyllic rolling
hills of derbyshire, England,

A surprising discovery has been unearthed

After 150 years.

Turner: He hid it.

And he hid it a little bit too well.

Narrator: How has this subterranean space

Produced a precious mineral
found nowhere else in the world?

Gunn: Less than 20
people have ever been down

In that part of the cave.

More people have been to the moon.

Narrator: So precious that
it's owned and cherished

By american presidents and british royalty.

♪

Narrator: Derbyshire county, britain.

The small town of castleton

Sits in the northern part of the county

And it's the only place in the world

Where a rare mineral has been found.

Around 300 million years ago
when this landscape was buried

2 miles beneath earth's surface.

An extraordinary process occurred.

Super-hot liquid minerals
were deposited and crystallized

As veins within the cavities
of this carboniferous limestone.

Known today as blue john, it has
never been found anywhere else.

Dr. Noel worley is a geologist and expert

On this uncommon geologic specimen.

Blue john is calcium fluoride,

Which is a mineral called fluorite.

Narrator: Ordinary white fluorite

Is found all over the world,

But blue john is scientifically unique

And is only found in treak cliff hill,

A small mountain approximately
a quarter of a mile across.

Wow.

Well, this is like a geologist's toy shop.

And I've got all the toys.

Wonderful piece of blue john.

Beautiful. That is quite outstanding.

Narrator: Despite much investigation,

Geologists remain uncertain

About the origin of blue john's color.

One hypothesis suggests that
atoms in the fluorite molecules

May have somehow been
disturbed to create this unique color,

Which can range from blue to yellow.

Worley: We believe that the
blue color here has been produced

As a consequence of the irradiation

Of the layers of fluorite
within the cavities.

Narrator: The origin of blue john's name

Is also shrouded in mystery.

Some believe it comes from
when it was exported to France

In the 18th century.

The colors of the mineral
...blue and yellow...

When pronounced in
french are bleu and jaune.

Blue john and treak cliff cavern

Aren't just of interest to geologists.

Professor john gunn
of birmingham university

Is a speleologist, a cave scientist.

He has found evidence

That the way the caves
were formed is unique.

Gunn: We believe that
treak cliff cavern is formed

In a rather special way,
not by water descending,

But by water actually coming up.

And we call this hypogenic speleogenesis.

So the water rising up is forming the cave.

Narrator: But forming a cave is a process

That doesn't happen overnight.

Gunn: Before you have a cave,
you have a conduit, these pipes.

And the difference is
that a conduit is too small

For a human to get into,

But it's perfectly fine for
water to move through it.

So we have these conduits
way back 300 million years ago.

A cave is simply a conduit
that's grown big enough

That humans can go in there.

Narrator: What happened next
is the secret behind blue john.

Then we had a phase when the rising fluids

Were mineralizing fluids

And they brought in the fluorite minerals,

One of which is blue john.

And those mineralizing
fluids were also opening out

And started to form the
present treak cliff cavern.

Narrator: Even today,
the system is evolving

And scientists are unearthing new finds.

Discovered in 2014,

John is exploring a newly
found series of caves

Called the hidden depths.

Gunn: It's always a thrill
in going into somewhere

That very few people have been
in, some newly discovered cave.

Those chambers, they've got
the blue john mineralization.

So this is some of the lowest elevation

Blue john mineralization
we've got in the area.

One of the really amazing
things about a place like this

Is how few people have been down there,

And we reckon that less than
20 people have ever been down

In that part of the cave.

More people have been to the moon.

♪

Narrator: It is believed

That blue john was first
discovered by accident

In the mid 18th century.

Gary ridley is treak cliff caverns manager

And is a blue john miner.

Ridley: The original miners
that discovered these caves

Were actually lead miners looking for lead.

And when they broke
through into these caves,

They found very little lead at all.

Nowadays, you can see just
these empty passageways.

Back then they would have
been absolutely full of blue john.

Narrator: Blue john became fashionable

During the regency
period of the early 1800s

When it was much in demand
for ornamental vases and columns.

Peak prices for the blue john antiques

Reached tens of thousands
of dollars in auction.

In 300 years of mining on treak cliff hill,

About 2,000 tons of blue john

Has been extracted from 15 so-called veins.

Each has a distinctive color and form.

Most of the blue john veins are
very different from each other.

And 9 times out of 10, when you see a piece

Of blue john jewelry or an ornament,

You can tell exactly
which vein it's come from

Just by looking at it.

Narrator: Treak cliff cavern
and its blue john deposits

Run just 500 feet into the limestone rock.

So mining here has
never been on a large scale

Requiring explosives.

Each piece of blue john
has been carefully extracted

In the same way for centuries.

The mining methods would
have been called plug and feather.

Until quite recently, we used to still use

The plug and feather method.

You would have two miners

And one would have had a drill bit,

Quite a long drill steel

And he would have held it on his shoulder.

And the other miner would stand behind

And he'd whack the end of the steel.

And every time he whacked it,

The guy in front would twist the steel.

And this must have taken absolutely hours

To drill these holes.

Narrator: The busiest
period of blue john mining

Was in the 18th century

When treak cliff hill was worth
in today's money over $200,000

And about 20 tons per year was extracted.

Ridley: Once the blue
john industry had taken off,

Of course, everybody
wants to get in on the act.

Probably at its height, there
would have been as many

As 20 little operations going
on on this one little hillside.

Narrator: But the blue john operation

Was about to get even bigger
with an amazing new discovery.

Narrator: When treak cliff hill,

Home of the rare blue john mineral,

Was taken over by the
harrison family in 1945,

The previous tenant, john royce,

Showed peter harrison
around the witch's cave

And suggested he had
discovered an unmined part

Of the upper treak cliff blue vein.

Peter's grandson john is
now part of the family business.

Turner: My granddad was told by john royce

That there was a vein of
stone that he wanted to dig out.

Narrator: But john royce died

Before peter discovered anymore.

Granddad was never told
whether it was a vein still in the wall

Or loose rock ready to be carried out.

Narrator: Despite huge efforts,

Peter couldn't find the
mysterious blue john deposit.

It became known as the lost vein,

But then 68 years later in 2013,

Miner gary ridley was
showing peter's grandson john

How to search for new veins.

And using a pick and
shovel on the soft clay,

They stumbled across something exciting.

Treak cliff cavern in derbyshire, England,

Has two working mines

Containing the rare blue john mineral.

In 2013, workers came across a new deposit,

Which they thought could be a
lost vein of the precious stone.

Turner: About half an hour into digging,

I discovered this vein in the wall,

Which was telltale signs of hidden vein.

There was carpet,
sticks, stones to hide it.

Narrator: They rediscovered
the lost blue john deposit

The original owner of
the mine had uncovered.

Turner: He hid it, and
he hid it a little bit too well.

Yeah, we had about four
or five tons of stone out of it.

Narrator: Two years later in 2015,

Gary was testing out a new method

For mining using a stone chain saw

In an area of the cavern
he'd never dug before.

Ridley: At first, I was
drilling into limestone.

It's quite hard to drill and the water

That was coming back from
the chain was very white,

So I knew we were in limestone.

And then after a few minutes,

The color of the water started to change,

And the saw started to plunge
quite quickly into the wall,

So I knew we were in blue john.

Once I got a piece
outside and cleaned it up,

I realized what we got
was a completely new vein.

Narrator: Unlike the
discovery of the lost vein,

Gary had found an entirely
new variety of blue john

And the first in over 150 years.

I then thought, "well, how much is this?"

We brought a jet washer in

And we started cleaning the walls down

And then we could see that the vein itself

Is traveling into the rock

And it was twisting up
and around the corner.

So there's a fair bit to go at

And it should keep us
going for quite a few years.

The pattern really stands out
no matter whatever you put it in.

And, see, it's a great vein to work with.

Narrator: Gary's meeting
geologist noel worley

To show him an example of his ridley vein.

Worley: Beautiful piece of ridley vein.

You can see the bounding
more clearly on this side.

You can see that here,

The blue john grew in this direction,

Just the curves and waves

In the bounding here that face upwards.

You can see there's a
lot more yellow in this vein

Than the other veins as well,

And probably two close
bands about halfway down.

The first time it's seen the light of day

In probably 300 million years.

The ridley vein is the
15th to be discovered.

The mineral is so scarce that today,

There are only two working
blue john mines here.

Less than one ton of blue john

Is mined from treak cliff every year.

Yet with the turn of the 21st century

And new veins being found,

It's starting to make a comeback.

People like john turner are
working with the mineral again

And large antique vases have recently sold

For enormous prices at auction houses.

Blue john is rare enough that,

Although it will never be a major industry,

Its role within the
decorative arts is cemented.