Unearthed (2016–…): Season 1, Episode 5 - House of Holy Relics - full transcript

The great
gothic cathedrals of Europe,

soaring medieval skyscrapers
that hold age-old secrets.

How did their creators
build so high

using only simple tools?

What beliefs inspired them
to reach for the sky?

It is an incredible building.

The height, the footprint,
the presence...

It's really spectacular.

And can new technology
unlock the secret science

that protects these stone giants
from disaster?

They had to be afraid



that the earth pressure would
bring the pits to collapse.

The only way
to solve these mysteries

is to blow apart these mighty,
medieval megastructures

stone by stone.

Diving deep through their walls,
vaults, and foundations

will help us unearth the
astonishing engineering secrets

at the heart
of these age-old wonders.

captions paid for by
discovery communications

the German city of Cologne

on the banks
of the mighty rhine river...

This is the home of the world's
most ambitious megastructure.

Cologne cathedral...

a mysterious monument that
began life in the middle ages.

750 years ago,
the people of this city



embarked on a colossal challenge

to build the tallest cathedral
of the day...

20 times higher than
the wooden buildings in town.

The sheer scale of this church

astounds modern experts
who try to unlock its secrets.

The amazing thing
about the Cologne cathedral is,

if you go back in time,
someone actually had the vision

to design and conceive
a building of this size,

and it's spectacular.

Cologne cathedral
is a 130,000-ton stone giant.

There's enough glass
in the walls

to clad a 30-story skyscraper.

Huge stone ribs
prop up the ceiling...

as well
as the 600-ton lead roof.

Stretching nearly 525 feet
into the sky,

two enormous towers
once made this church

the tallest building on earth.

So how did they pull off
this medieval marvel?

Historians
know surprisingly little

about what actually went on

during the early days
of Cologne's construction.

Few records have survived.

Now architect Doug Pritchard

is rediscovering
how the cathedral was built

by stripping it apart
stone by stone.

Doug's got the perfect tool
to do this...

A digital laser scanner.

This machine will allow him
to reveal the building

in unprecedented
forensic detail.

The scanner
is really quite incredible.

It can generate

approximately 1 million
dimension points per second.

The way that the scanner works

is that it does
a 360-degree sweep.

It will show things like
the depth of the vaults,

the size of the columns,
in a very precise way.

We take all that data together,

and the result is you have
a 3D map of the cathedral.

Today, Doug's adding

another important piece
to his puzzle.

Guten tag.

Hi.

He's on his way
to the central balcony.

If he can use scanning

to expose the cathedral's
underlying structure,

he can start to dissect
how it works.

One of the great
things about laser scanning

is that you could
pull the data apart.

Let's use the scanned data
to explain the architecture...

How the building stands up,
how the engineering works.

Doug's scanner
fires an invisible laser beam

as far away as 614 feet.

It records each time
the beam hits something solid

and bounces back...

and then turns this data
into incredibly detailed images

so that Doug can study
the structure from every angle.

In total, right now,
we're at about 660 scans.

Probably, by the end of this
week, add in another 20 or 30.

Doug now needs
to crunch a huge volume of data.

But he can already start to see
the master plan

of the people who built
this incredible monument.

The two tall towers
are visible for miles.

At the top, the spires are open
to cut down wind resistance.

And at the bottom,
the walls are rock-solid

to bear the enormous weight
of the towers.

But the church behind
is completely different.

Under the skin sits a skeleton
of slender stone arches.

Incredibly, it looks like
the core of a modern skyscraper,

yet this is the brainchild
of medieval master builders...

Men who lived 700 years ago.

So how did Cologne citizens
even begin to imagine

that such a tall building
could be possible?

200 miles away,
in northern France,

another team hunts for clues
at an even older cathedral.

This is Amiens...
The blueprint for Cologne.

This soaring church
has dominated the city's skyline

for nearly 800 years.

It's the tallest
complete cathedral in France.

Investigator Guillaume Caron
uses laser technology

to unlock how
Cologne's predecessor was built.

I was born, actually,
in the city,

so I know the symbolic aspect
of this cathedral.

Guillaume is hoping
to find tiny clues

that might help reconstruct
Amiens' lost original design.

Currently, there is not
any actual map of the cathedral,

so what we are doing
with this kind of device

is to measure it very precisely

in order to have the first real,
actual map of the cathedral.

Amiens' construction
began in 1220.

It's one of a handful
of cathedrals close to Paris

whose architects dreamed
of building closer to god.

They wanted to build the highest
and the widest cathedral

because at that time
in the middle ages,

it was like a race between
the different cities in France

to build
the most important cathedral.

Guillaume's scans reveal

that the central arch
is 131 feet high,

but the columns
are surprisingly thin.

From this scan preview,

we can look at the details that
were acquired by the device.

For instance, the columns here
in the transept.

But until the 12th century,

columns this tall and slender
would have been too weak

to support
such an enormous building.

So how did French architects
solve a puzzle

that has baffled even the great
builders of ancient Rome?

The key
is in the shape of the arches.

In a classical Roman arch,

the stones at the top push
sideways against the columns.

As you build higher,
they start to buckle...

And the ceiling will collapse.

But French engineers realized

that if you make the arch
pointed...

The forces now flow down towards
the strong base of the column.

Now the same columns
can take more weight.

The arch can be much taller
and the church much bigger.

Amiens, with its pointed arches,

showed Cologne citizens
a glimpse of what was possible.

But what drove the Germans
to build even higher?

The secret lies at the heart
of Cologne cathedral,

inside this golden shrine.

Some believe it holds the bones
of the three wise men.

Peter Fussenich

is the cathedral's
current chief architect.

He oversees an army
of more than 70 people

who keep this building running.

Today, the church attracts
6 million visitors a year.

But Peter thinks
that in the middle ages,

it was also this tomb
that was the star attraction.

The shrine is,
of course, one of the reasons

why they built Cologne cathedral
in the first place.

It's less the shrine...
That was built later.

It's more what's inside it.

I'm talking about the bones
of the three wise men.

This holy relic
arrived in Cologne in 1164

and immediately triggered a huge
stream of pilgrims to the city.

That meant that very quickly,
the old church became too small,

which is why they had to build
a bigger cathedral.

This mysterious holy shrine

inspired Cologne's founders to
start work on a cathedral so big

that they knew they would never
see it finished

in their lifetimes.

This is something

that's still immensely
fascinating for us today.

Cologne cathedral

is one of humanity's first-ever
multigenerational projects...

Something you have to hand down
to the next generation

and have faith that they will
actually carry on building it.

These men hoped that
their children and grandchildren

could overcome
the next huge obstacle...

how would they build a church
with enough room

for 20,000 worshippers made
from fragile walls of glass?

Cologne cathedral is a
mysterious medieval skyscraper.

It covers 86,000 square feet.

How did her creators
illuminate a church this big

with heavenly light...

Hundreds of years
before electricity?

The answers are hidden deep

within the fabric
of the cathedral.

The towers rest on thick,
stone pillars

to stop them from collapsing.

But the main hall of the church
is much more open.

There's enough glass here
to cover a football field.

The upper walls in the middle
are almost entirely glass,

just inches thick.

And they're crowned
by a massive lead roof.

So how did medieval engineers
construct windows so big,

so fragile, yet so strong?

In the middle ages,

craftsmen had no way to make
huge, flat sheets of glass.

Ulrike brinkmann studies
the ingenious solution

that allowed them to push
the boundaries of technology.

Medieval glassmakers divided up
each window into panels.

They made them from
tiny stained-glass fragments

held together by lead.

Medieval glass is blown
by mouth, by glassmakers.

They have a large glass pipe,

and so the size
of the glass panels

that are used for
the glass painters is limited.

You see, the very, very dark
deposits on the glasses...

In this case, luckily,
they can be easily removed.

The fragments
still look dark after cleaning,

but they come alive
in the light.

Light was a material
in the medieval understanding,

and how light fought through
another material, like glass,

without disturbing the glass,
was without any explanation.

These exquisite details

would have been imperceptible

to worshippers
on the cathedral floor.

But this kaleidoscope of glass
creates the impression

of a church
reaching towards heaven.

Entering the
cathedral in medieval times...

It must have been breathtaking.

The sun falling through
and lighting the interior...

This was very impressive.

They are still
breathtaking today,

and even more in those days,

when people used to live
in small and dark houses.

But the extreme height
of these windows

creates a serious problem.

Pointed arches help make taller,
more elegant churches

with big windows
from top to bottom.

But build too high,
and the structure collapses.

Supporting walls,
called buttresses,

could help take the strain,

only they'd block out light
and cut across the aisles.

Medieval engineers discovered

that if they build columns
on the outside

with high beams reaching across,

they could build what are known
as flying buttresses.

Now they could install
huge windows

to bring them closer to god
and let in heavenly light.

These flying buttresses

help support the walls and roof
from the outside,

but what stops the ceiling from
crashing down inside the church?

How does it appear
to hang in mid air?

Wolfgang kupper is one of 20
expert stonemasons at Cologne.

He knows that working
with the soft limestone

requires complete precision.

With this saw blade I borrowed

from the metal workers,
I can easily cut into the stone.

The stonemasons
are like surgeons

who care for
a 750-year-old patient.

Today,
Wolfgang has the challenge

of replacing a stone block
called a baldachin.

At the moment,
I'm working on this finial.

I'll have to carve out
these gaps

and remove the material
in between

to bring out these leaves...
Extremely small features.

The original stone
that formed part of the wall

is damaged beyond repair.

This was damaged
in world war ii.

The front part of it
is completely gone.

All that's left is the back end.

Carving this copy

will take Wolfgang
a year and a half to finish.

Did Wolfgang's
medieval predecessors'

meticulous attention to detail

contribute to the cathedral's
incredible durability?

Stonemasons at Cologne cathedral

are revealing
the innovative design

of this soaring
medieval skyscraper.

Instead of thick, stone walls
to carry the ceiling,

they carved pointed arches

and joined them together
like a rib cage.

In between, they put
just a thin layer of bricks

that forms a smooth ceiling
called a rib vault.

Slender columns
channel the weight of this vault

down to the ground.

This way, the ceiling
doesn't need support.

It supports itself.

The forces on this
vaulted ceiling are enormous.

And just a few stones
out of place can spell disaster.

The older cathedral of Amiens,
in France,

reveals the risks
of this audacious design.

Laser-scanning expert
Guillaume caron

is at Amiens to investigate
damage to the rib vaults.

We have, on the ceiling,
a big crack.

That's where, with our laser
scanner, we are able to measure.

This is the scanning result.

Guillaume discovers
that this crack

is about two inches wide.

There is also other cracks

inside the main nave
of the cathedral,

so on the top
of this tall window.

Guillaume can't say exactly

what's causing every crack.

But experts think that Amiens
has a serious design flaw.

Outside, the flying buttresses
are too high

and can't take the strain
of the roof.

So the sides have buckled,
tearing the rib vaults apart.

So is the damage getting worse?

From our latest results,

we measured that this crack
is about five centimeters,

and we compared that

with measures we made
four years before.

Actually, there is no increasing
of this thickness,

and this is good news
for the cathedral.

In Germany,
at Cologne cathedral,

the ceiling looks perfect.

But is it?

Doug Pritchard ventures
inside the roof to investigate.

He wants to laser-scan
Cologne's rib vault from above.

Right now,
we're between the crossing

and the older part
of the building... the choir.

The way that the scanning
is gonna work

is I'll have the scanner

positioned all the way around
this opening area here,

and with that data,

I'll take the data from below
that was scanned earlier

and combine the two.

And with that,

I'm able to virtually
slice through the cathedral.

Doug hopes his scans

will expose
the cathedral's inner workings

and show them like never before.

I think
this is a fantastic image

in that it clearly, clearly
explains the architecture

of the cathedral.

The finished 3D image

captures the cathedral
with extreme accuracy.

And what I focused on here is
where we're currently standing,

and what's interesting
is the rib vaults

are actually almost like
a thin membrane,

but the actual engineering
and structure

is being picked up
by the pointed arches.

You have the columns,

which are taking the weight down
to the foundation.

You also have
the flying buttresses,

which are pressing inward
slightly,

and so they're all in Harmony

in terms of how the structure
of the cathedral works.

Doug's scans present
an even more intriguing mystery.

How did ancient engineers
build a rib vault

over 131 above their heads
without it crashing down?

Investigators think
that the builders first put up

wooden scaffolds all the way
to the top of the arches.

They stacked stone blocks on top

to build the ribs
with extreme precision...

so the centerpiece
would fit perfectly.

Then they filled the gaps
between the ribs

with lightweight bricks
and covered them with mortar.

Finally, they removed
the wooden scaffold,

praying that their ceiling
would hold.

Cologne's builders had created
a perfectly balanced skyscraper

hundreds of years before
those of the modern era.

But how has
this colossal cathedral

survived centuries of wind,
rain, and natural disaster?

Cologne cathedral
is a remarkable survivor.

This stone giant

stands in one of Europe's
most active earthquake regions.

More than 120 quakes

have hit the surrounding area
over the last 300 years,

causing modern buildings
to crumble.

So what's the secret?

How has
this mysterious structure

survived life
in the danger zone?

Klaus-G. Hinzen
is a seismologist

at the university of Cologne.

He leads a team of specialists
to the cathedral roof.

They've come to retrieve data

revealing how the cathedral
reacts during an earthquake.

We started to monitor
the cathedral in 2006.

From time to time,
we have to do maintenance

and to see
how the station is working.

Can you give
the control-f?

These instruments
are motion sensors

that will pick up
even the tiniest movement

in the fabric of the church.

On the left,
on the small screen here,

we see the ground motion
that is just being recorded

here at this moment,

and we can see
that it is actually working.

I just have to stamp
a little bit with my foot.

You see, it is rather sensitive.

We are a couple of meters away
from the sensor,

but anyway,
you pick up the signal.

This equipment is helping Klaus

to predict what would happen
in a big quake.

We have had
several strong earthquakes

with magnitudes between 6.5
and 7

in the past 20,000, 30,000 years
in the area.

And geologically,
this is a very short time span,

and such an earthquake
could happen any time.

It could hit today or next week.

He fears that a major earthquake

could shatter
these ceiling vaults.

But Klaus' work reveals

that the towers would behave
very differently.

Here we see a recording
example of a real earthquake.

It was about 90 kilometers away
from the cathedral

and had a magnitude of 4.5.

The red traces
are the ones that we recorded

in the basement
of the cathedral,

which basically
is the input signal,

which comes into the building,
and for comparison,

the blue signals
that we see here...

This is the motion of the tower.

We see the tower
starts swinging back and forth,

and this motion of the tower,
then, lasts for several minutes,

that we can record it.

It's an astonishing mystery.

How did Cologne's architects
create towers

that swing like pendulums

instead of crumbling
to the ground?

Even with
all these slender columns,

this building
is no featherweight.

Medieval engineers
took care of this weight

with secret structures
hidden underground.

They layered
120,000 tons of rocks

into super massive
foundation pillars

stretching deep underground.

Just as much stone
lies beneath as soars above,

balancing this cathedral
perfectly.

Cologne's founders
protected their cathedral

with deep foundations,

but in the middle ages,

most people saw earthquakes
as a punishment from god

and thought only prayers
could prevent them.

So did the cathedral's builders
really understand

the true forces of nature
at work?

Archaeologist Ruth Stinnesbeck
investigates what they knew

about the ground
they were building on.

Her quest takes her down
to an archaeological dig

underneath the cathedral floor.

Here, investigators
were astonished to discover

that this foundation pillar
goes down 52 feet.

It's as deep as the pillars

that support
the empire state building.

But what really shocked them is
what they found at the bottom.

Oh, yes.
That's the beep.

Water.

So why did the medieval diggers

risk flooding
their own construction site?

Ruth thinks it's because
they discovered

an even greater danger...

Sand.

The city of Cologne
and also the cathedral

is just standing on sand
and gravel,

and that's the sand
we also have down here.

You look, it's nothing solid,
just sand.

The builders here worried

that the cathedral would sink
into Cologne's soft sand.

So they decided to push their
foundations as deep as possible

to minimize any risk.

It must have been like
digging on a beach.

So how did they do it?

If workers
tried to excavate a hole

wide enough and deep enough
in one try,

the loose sand would have
caved in and crushed them.

So they dug
only in shallow steps...

Shoring up the sides
with wooden boards,

stopping just before
the water level.

They piled in layers
of volcanic rocks and mortar

to build up mighty stone pillars
over five stories tall.

These formed
rock-solid foundations,

supporting 120,000 tons of stone
to this very day.

Archaeologists have unearthed
the startling remains

of this ancient
construction site.

Over here,
we have the foundation

of one of the pillars
upstairs in the cathedral,

and what we see
is a mortar surface.

Ruth believes
that these splinters

are the remains
of the wooden boards

the builders used
to hold back the sand.

You see, one plank
starts over here to there,

and the next plank
from over here...

To here.

When I look at the wood,

I try to imagine
how the people must have felt

when they worked down here in
those very deep and dark pits,

and yeah, they had to be afraid
that the earth pressure

would bring the pits
to collapse,

and only those planks
would prevent it

from such a catastrophe.

And so I think
when you stand down here,

you can feel how the people
might have felt at that time.

Archaeologists like Ruth

continue to investigate
this intriguing underworld.

But there's another surprise
above ground.

Behind the beautiful
vaulted ceiling

lies a strange structure.

What could it be?

Cologne cathedral
is the most ambitious

medieval cathedral in the world.

This towering structure conceals
many surprising secrets.

There's much more to it
than meets the eye.

Under the hood
of this stone giant

hides a structure
that looks out of place.

It's a gigantic framework
of slender, wrought-iron struts

that hold up the 600-ton roof.

Until the Eiffel Tower,

this was the most advanced
iron construction on the planet.

So what is this metal marvel

doing inside
a medieval building?

Drawings and chronicles record
the construction work

on the cathedral
ground to a halt in 1530.

It didn't start up again
for more than 300 years.

So how did
19th-century craftsmen

know how to finish the building?

Chief architect Peter fussenich
uncovers the answer...

a faded 13th-century design
for the two towers

that was once lost

but rediscovered by chance
nearly 600 years later.

The architects
of Cologne cathedral

in the 19th century

were very lucky to find
that medieval plan,

to have the possibility
to build the facade

so that they could finally
finish the dreams

of the medieval architects.

The sketch, called "plan f",

looks like a modern blueprint,

but it has no dimensions,
no instructions.

This "plan f" was not meant
as a construction plan.

It was a plan to convince those
who financed this cathedral,

of course.

So how good a job did
the 19th-century builders do?

Stone restorer Sophie Hoepner
belongs to an army of experts

who uncover
how the final builders

had to make compromises.

Sophie and her colleagues
are on their way

to fix a problem
with the flying buttresses

built in the 19th century.

The work of a stone restorer

is maybe comparable to,
in medicine, a doctor.

The medieval builders

preferred to use a hard stone
called trachyte,

but the rock in these flying
buttresses from the 19th century

is soft sandstone.

And it's already
starting to crumble.

What we can see here,
some deteriorated area.

Here we have all the rain
is coming from above

and just washing.

You see, it's much dryer,

and there is
a collection of dirt.

You get black appearing because
of the pollution in the air,

and these parts
where the stone is like sand,

it gets washed down.

And that's why it's much clearer
than the rest of the stone.

Sophie needs to know
how bad the damage is.

So her first task is to test
how the stone reacts to rain.

If you put this drop on,
you see,

the stone is like a sponge.

During the rain, the water goes
into the pores of the stone,

and when the stone dries,

every material
that was in the water goes out

and is staying on the surface.

Sophie can treat
some of the sandstone

with a special
waterproofing chemical.

On this surface,
there's an hydrophobic agent,

so when I put a water drop,
you can see, it stays.

But some stones
can be rotten to the core

with no visible signs
on the outside.

So the team decides to probe
the inside of the buttresses

with a special drill
hooked up to a computer.

Sophie's colleague Jasper
drills in to the soft sandstone.

The computer measures
the resistance to the drill,

revealing weaknesses
in the stone.

What will the results tell us?

At the Cologne cathedral,

a restoration team must repair
and replace this buttress.

Not even stone lasts forever.

We will use
some consolidant agent

to make the stone hard again,

and then we test
whether it worked.

So why did modern builders

use such poor-quality stone?

The problem was they couldn't
find enough good material

to finish such an enormous task.

When they started building,

all that existed
was the back end of the church,

the ruin of the south tower,

and a huge,
half-filled gap in the middle.

Just to get this far,

medieval builders had ripped
the top off a nearby mountain.

But this source of stone
ran dry.

So 19th-century builders

had to find thousands of tons
of sandstone

from many different sources
all over Germany.

Here, they used the highest
scaffold of the time

to place the stones

and finish the cathedral
in just 38 years.

So did the builders
sacrifice quality

in their race
to finish the cathedral?

Local legend says

there's something not
quite right about the towers.

Architect Doug Pritchard
is going to use his scanner

to measure just how tall
they really are.

There is a certain mystery

regarding the heights
of the two towers.

Are they exactly the same?

Is one higher than the other?

And that's what the scanning
will confirm.

Doug hitches a ride

through the core
of the north tower.

We're up on the north
tower at the 100-meter level,

and what I'm going to do is set
up the tripod and scanner inside

so that we can capture the
entire interior of the tower.

This is the first time

that anyone has measured
the towers with such accuracy.

What I'm able to do
is do a 360-degree scan

of the entire interior
of the tower,

and that will give me
sub-centimeter-level data.

The scanner can generate

over 1 million dimension points
in a second,

so within 15 minutes,

we're gonna have
a massive amount of information.

Doug puts the scanner to work.

The final stone was laid on top
of the south tower in 1880.

Construction had lasted
632 years and 2 months.

Doug makes a discovery
that astonishes even him.

Looking at the data,

comparing the height of the
south tower and the north tower,

they are almost
exactly the same height.

The south tower is just
slightly, slightly taller

than the north...

Only by 4 centimeters,
which is really remarkable.

Also, if you consider
the age of the two towers,

really tells you about
the craftsmanship

and the skills of the people
that built this building.

Doug's scans are a precise,

digital copy of the cathedral.

They reveal
how generations of craftsmen

remained true to a design
that's more than 700 years old.

When you compare this building
with contemporary buildings,

what is truly amazing here is

that everything has been made
by hand, by craftsmen.

Everything from individual
stones to the entire structure,

and that really is significant.

It isn't manufactured off site.

It isn't
coming out of a factory.

This was done by hand.

The vision behind it,

by the people that wanted
this built, is incredible.

It is
a really significant building

in its size and its beauty
and its grandeur.

Cologne cathedral,
like its predecessor at Amiens,

is an extraordinary achievement.

Today,
millions of people pass through

their richly-decorated doors to
gaze at the first skyscrapers,

which took many lifetimes
to complete.

Cologne cathedral continues

to inspire awe
and devotion today...

thanks to its soaring
gothic arches,

which revolutionized
architecture...

and a dazzling interior
awash with sunlight

from thousands of shards
of painted glass.

Cologne's sheer size
and complexity

continue to amaze engineers
today.

Its two iconic towers
stand out like beacons...

Drawing visitors
from across the world

to this medieval wonder.