Nova (1974–…): Season 42, Episode 6 - Hagia Sophia: Istanbul's Mystery - full transcript

NARRATOR:
Hagia Sophia

For nearly a thousand years,

the largest enclosed building
on earth

Its heavenly dome
soars 180 feet high,

supported by arches
that inspire awe to this day

for their strength
and resilience

When it opened, gold mosaics
covered over four acres

of its walls and ceilings

How did ancient builders
construct

such a magnificent monument?

ROBERT OUSTERHOUT:
There's nothing practical
about Hagia Sophia



It's all innovation

NARRATOR:
Built nearly 1,500 years ago
in Constantinople...

Modern day Istanbul...
Hagia Sophia has survived

clashing empires by transforming
from church to mosque to museum

JOAN BRANHAM:
Hagia Sophia carries
both the history of Christianity

and Islam within its walls

NARRATOR:
Most remarkably,
Hagia Sophia has survived

centuries of city-busting
earthquakes

Did ancient architects
actually design

an earthquake-proof structure?

Or will the next big quake
bring Hagia Sophia down?

To find out, a team of engineers
is monitoring the building

and constructing a giant model,

placing it on
a hydraulic platform,



and hitting it with powerful
simulated earthquakes

Can they unlock Hagia Sophia's
seismic secrets

before Istanbul's next
big quake?

(klaxon blaring)

ESER CAKTI:
There is always
this fear factor,

this fear of seeing
unexpected collapses

Right now on NOVA...

"Hagia Sophia:
Istanbul's Ancient Mystery"

NARRATOR:
Hagia Sophia,
completed in the year 537,

is one of the most magnificent
buildings ever constructed

Its size alone is awe-inspiring

Only the pyramids surpassed it
in height

for almost a thousand years

Its ceiling is a glittering
gold dome

that spans over 100 feet across

and soars 180 feet above
its marble floor

The Statue of Liberty can fit
beneath its dome

with room to spare

How did ancient builders
nearly 1,500 years ago

construct such a gigantic dome?

Since its completion, Hagia
Sophia has withstood

the rise and fall of empires

It has transformed
from Christian church

to Muslim mosque
to secular museum

BRANHAM:
Hagia Sophia influences
a number of mosques

and it became a model for
Christian churches as well

Its innovative, ambitious design

and its monumental scale

speak to people across cultures,
faiths and religions

NARRATOR:
How can one building be a symbol
for two different religions

and continue to inspire people
to this day?

KORAY DURAK:
Hagia Sophia is a unique
building

There are only a few structures
in the world

that present different layers of
history in the last 2,000 years

NARRATOR:
But perhaps the greatest mystery
is why it still stands at all

For Hagia Sophia is in Istanbul,

known as Constantinople
in ancient times

The city straddles two
continents... Europe and Asia...

And a major earthquake fault

Over the last century,

the North Anatolian fault has
unleashed a series of quakes

The most recent, in 1999,
was just 60 miles from Istanbul

And it was devastating,

leveling hundreds of buildings
across the city

and killing thousands of people

MUSTAFA ERDIK:
The damage caused by the '99
earthquake was extensive

Plus, there is a huge
human loss, about

we lost about 17,000 people

NARRATOR:
But somehow, Hagia Sophia
is still standing

In fact, Hagia Sophia has
withstood every major earthquake

for nearly 1,500 years

What is the secret
to its survival?

As Istanbul braces
for the next big one,

a team of engineers searches
for answers

by building an enormous scale
model

and hitting it with a series
of simulated earthquakes

In the process they will uncover
the building's strengths

and weaknesses

weaknesses that could
ultimately threaten

Hagia Sophia's survival

ESER CAKTI:

NARRATOR:
Eser Cakti is director of the
earthquake engineering lab

at Bogazici University

She is tasked with monitoring
the structural integrity

of Hagia Sophia

Slanted floors and leaning
columns may appear alarming

But Cakti is most concerned

about Hagia Sophia's
core structure

That core structure comes down
to a few key elements...

The enormous dome resting on
four huge arches,

which in turn are buttressed
by four giant piers

and two semi-domes

Of particular concern
are the four arches

If any fail,
the dome could collapse

To monitor the arches,

her team has placed sensors
at strategic points

The sensors can detect
the faintest of movements

CAKTI:
The data that we obtain from
here is very important

in terms of understanding the
general structural behavior

of this huge building

NARRATOR:
This information is transmitted
to screens

at Istanbul's Earthquake Center

Each of the multicolored lines
represents vibrations

detected by a motion sensor

Normally the lines
are nearly flat

But when an earthquake strikes,
there's a dramatic spike

From results of years
of monitoring,

Cakti sees two places
of potential danger

CAKTI:
These are the vertical
vibrations on both the arches

on the east and west side

NARRATOR:
Two of the great arches

are moving more than they have
in the past,

which could have serious
implications for the future

If an earthquake
comes strong enough,

I think there is a real chance
it can receive damage

NARRATOR:
Will the next big quake

finally topple Hagia Sophia?

NARRATOR:
To investigate what danger
Hagia Sophia might be in,

Cakti is turning to a tried
and true technique...

A seismic shake table test

It's worked before

In 2012, Cakti teamed up with
engineering team Eren Kalafat

and Korhan Oral to analyze
the structural integrity

of the Mustafa Pasha mosque
in Macedonia

They built this
large-scale model,

placed it on a motorized
steel platform,

then shook it violently
to simulate an earthquake

The idea is that wherever damage
appears on the model

is where damage would appear
on the actual building,

giving engineers important
insights to protect

the real structure

It worked for
the Mustafa Pasha mosque,

but will it work
with Hagia Sophia,

a building larger,
heavier and more complex?

The model team has doubts

The main issue is scale

The core structure must be
precisely scaled down

for the shake table experiment
to be accurate

If Cakti chooses
a scale of 10:1,

the dome, at just over
100 feet wide,

would be 10 feet wide
on the model

But that's still too big
for the shake table

CAKTI:
Each shake table has a capacity

in terms of its dimensions

and in terms of the power
that it can create

NARRATOR:
The capacity of this shake table
is ten tons

The scale Cakti wants to use
will make the model too big,

so she must scale it down

After intense recalculations
it looks like a 26:1 scale

could work, at least on paper

CAKTI:
We are always nervous

at the shake table,
whether it will work

NARRATOR:
The scale model is
an ambitious project

with no guarantee of success

But it pales in comparison
to the challenge of building

the real Hagia Sophia

Who built Hagia Sophia, and why?

Hagia Sophia is built at
a major crossroad in history...

The decline of the Roman Empire

and the rise of
the Byzantine Empire

In 324 A D, after Rome
is ravaged by civil war,

Emperor Constantine establishes
a new capital

in the city of Byzantium

It's renamed after him

He embraces a new religion,
Christianity,

and Constantinople becomes the
center of the Byzantine Empire

as Rome fades in importance

The empire thrives,
but in the early 6th century,

a power struggle erupts after a
new emperor ascends the throne...

Justinian

Riots break out,
challenging his authority

Theodora, his much younger wife
and rumored ex-courtesan,

persuades him to fight
rather than flee

OUSTERHOUT:
Justinian rallied
to the challenge

He called the rebels,

looking as if he was going to
meet their demands,

met them in the hippodrome,

had the doors closed and had
the army slaughter them all

NARRATOR:
Tens of thousands are killed and
Justinian emerges victorious

But during the riots, the rebels
burn down much of the city,

including an older imperial
church also called Hagia Sophia

This is all that remains

OUSTERHOUT:
Much of the city
of Constantinople

had been destroyed
in the great riots,

and this allowed Justinian
the opportunity to, in effect,

rebuild Constantinople and
the church of Hagia Sophia

in his own image

Justinian needed a building to
convey both his power as emperor

and piety as a Christian

So what to build?

Joan Branham is a professor
of art history

at Providence College

and an expert on how builders
design sacred space

She is at San Giovanni
Evangelista,

a church in Ravenna, Italy

Although rebuilt many times,
its floor plan dates

to when Christianity
becomes a state religion

BRANHAM:
For the first few centuries,

Christians worshiped in private,
in homes and small buildings

But this completely changes
in the fourth century

NARRATOR:
Christianity had been
an underground cult

and Christians persecuted

But when Christianity becomes
the official religion

of the Roman Empire, Christians
face a different problem

What should a church look like?

BRANHAM:
Early church builders looked
at Biblical prototypes

like the Temple of Solomon
described in the Hebrew Bible

But it's actually a
secular Roman building

that is adapted for
early Christian use

NARRATOR:
That building is the basilica,

used for courts of law
and other public gatherings

Its floor plan... a large central
nave flanked by two aisles,

and culminating in an apse...
Becomes the model for churches,

an ideal space for worshippers
to gather

Justinian embraces the church's
rectangular shape

to demonstrate his
Christian piety

But he still needs something to
symbolize his imperial power

He looks to the dome of the
Pantheon in Rome,

the ultimate symbol of the might
and glory of the Roman Empire

But the Pantheon's dome sits on
a thick circular base

Justinian wants his dome
to be centered

over a rectangular
Christian basilica

BRANHAM:
Justinian sets out
to do something

that has never been done before

He wanted to merge two
architectural structures

into a mammoth hybrid space

NARRATOR:
So where do you find builders
to create something on a scale

that's never been done before?

Justinian turns
to Greek mathematicians

AHMET CAKMAK:
Justinian hired Anthemius of
Tralles and Isidorus of Miletus

Both had experience as
mathematicians and physicists

and scientists of their day

They were asked to create

the most impressive, biggest
building ever built

NARRATOR:
Justinian puts these university
professors in charge

of 100 contractors
and 10,000 workers,

and gives them the entire
treasury

of the Byzantine Empire

The emperor is taking
a big gamble

OUSTERHOUT:
There's nothing practical
about Hagia Sophia

It's all innovation

It's geometric flights of fancy

beyond what a practical
architect would ever attempt

to build

NARRATOR:
Their first challenge is
how to support the dome

and still keep a huge space
for worshippers below

CAKMAK:
If they built walls or columns,

the space would not be open
like this

It would be much smaller
and narrower

In order to make it as large
and as heavenly as possible,

they need a big space

And that can only be
accomplished

by building large arches

NARRATOR:
A giant dome will need giant
arches to support it

CAKTI:
The original architects should
have been very concerned about

how to support this huge dome
over there

NARRATOR:
The team back at the earthquake
center face the same challenge

building their model

Will their arches be strong
enough to support the dome?

To find out, they add sacks
of cement

to simulate the weight
of the dome

Each bag weighs about 50 pounds,

and they expect the arch
to support about ten of them

But as the fifth bag is placed

Luckily nobody is hurt
as the arch collapses

with only about 200 pounds on it

CAKTI:
It collapsed before
we were expecting

the collapse to take place

I think that happened
because we didn't wait

for the mortar to set fully

NARRATOR:
While this might seem to be
a setback for the team,

Cakti insists this kind of
unanticipated collapse

illustrates one of
the main advantages

of building a physical model

CAKTI:
It is always interesting to see

the failure mechanism
in real life

When you do it on computers,

you develop an idea of how the
failure is going to happen

But it is only during
a test of this kind

where we see the
collapse pattern

NARRATOR:
The slow-motion replay
of the collapse

shows that the downward force
of the sacks

pushes the arch out sideways

The weight of the dome exerts
the same force on the arches

in the real Hagia Sophia

CAKMAK:
The arch wants to push out

and fall down

So you have to hold the arch
together like bookends

NARRATOR:
To create those bookends,

Anthemius and Isidorus,
the Greek mathematicians,

build four buttress piers...

Massive weights of brick and
mortar... and two semi-domes

These push back
against the arches,

canceling out the sideways force
caused by the dome

But Anthemius and Isidorus still
have one more problem to solve:

how to rest the dome on the tips
of the arches

CAKMAK:
The architects had to transition
from a circle to a square

This they accomplished

by building what is called
pendentives

It is this triangular shape

that fills in the corners
of the square

NARRATOR:
The pendentives together
with the arches

transform the circular base of
the dome into a square

And the semi-domes stretch
that square into a rectangle

Justinian has it all...

The classic rectangular shape
of the basilica

capped by the enormous
circular dome

Anthemius and Isidorus complete
Hagia Sophia in only six years

and do indeed spend nearly
the entire treasury

of the Byzantine Empire

In 537, Emperor Justinian
and his wife Theodora

unveil their church to the world

All who enter are awed
by its size

and the richness
of its decorations

Columns crowned by capitals
so finely carved

they look like lace

Floors and walls of marble
dazzle worshippers

with patterns of swirling colors

OUSTERHOUT:
Justinian brought marbles from
all parts of the empire

The great purple columns that we
see in the corners, for example,

come from the imperial quarries
of Egypt

Elsewhere in the building we see
stones brought from as far away

as the Pyrenees in Spain

NARRATOR:
An eyewitness account reports

that the dome looks "as though
it were suspended from heaven

by a golden chain"

Like the church before it,

Justinian christens this
monument "Hagia Sophia,"

which in Greek means
"holy wisdom"

But the dome that Justinian
first sees

is not the same dome that sits
atop Hagia Sophia today

Just 20 years after Hagia
Sophia's unveiling,

its dome collapses in a
catastrophic earthquake

OUSTERHOUT:
We really don't know what
Justinian did

when the first dome collapsed

We can imagine he wasn't
very happy

Fortunately for Isidorus
and Anthemius,

they were dead by that point

CAKMAK:
When the dome collapsed in 558,

the business of rebuilding it

was given to the architect
Isidorus the Younger,

a nephew of the original
architect

NARRATOR:
Cakmak believes Isidorus the
Younger redesigns the dome

To reduce its weight, he
installs 40 windows at its base

CAKMAK:
The windows serve two purposes

One is to get rid of the bricks
that you needed,

which add additional weight,
and to let light in

NARRATOR:
Hagia Sophia is put to the test

in at least another dozen
major earthquakes

The dome suffers two partial
collapses, which were repaired,

so visitors today cast their
eyes up to the same dome

built by Isidorus the Younger
nearly 1,500 years ago

But Hagia Sophia has withstood
more than just seismic activity

It's also been resilient
to cultural upheavals

600 years after Justinian,

Constantinople continues
to flourish,

but its riches inspire envy

In 1204, European Christian
Crusaders on their way

to the Holy Land sack the city
and loot treasures

from the Byzantine Christian
Hagia Sophia

Then a new religion challenges
the old order... Islam

Its forces lay siege to
Constantinople seven times

over eight centuries

Finally, in 1453, Sultan Mehmet
conquers the weakened city

and makes it the capital
of his Ottoman Empire

Mehmet enters the church of
Hagia Sophia on a Tuesday,

and by that Friday he is praying
in the mosque of Hagia Sophia

OUSTERHOUT:
For Mehmet the Conqueror,

Hagia Sophia was really
the ultimate conquest

That was the symbol he was after
for his new empire

NARRATOR:
But how can a church
become a mosque?

From an architectural
perspective, it isn't difficult

BRANHAM:
There was the addition
of the minbar

from which the imam
would give the sermon

The mihrab gave the sacred
direction orientation to Mecca

NARRATOR:
Later, the Ottomans
add large discs

calligraphied with sacred words
from the Koran,

plaster over Christian mosaics,

and outside construct minarets
for the call to prayer

But Hagia Sophia's vast dome

most easily makes the conversion

BRANHAM:
The dome itself had
religious meaning

for both Christian worshippers
and now Muslim worshippers

For both, it was a symbol
of the heavens

The structure at the heart
of Hagia Sophia...

The round dome
on the square base...

Works as powerfully for Islam
as it did for Christianity

Hagia Sophia is so admired
in the Islamic world,

it becomes the classic model

for mosques throughout
the Ottoman Empire

Today, Hagia Sophia is a museum,

a showcase of its religious
and cultural history

DURAK:
When you enter the building,

you look to your left and you
see a beautiful mosaic panel

from the Byzantine Empire

And you look at your right
and you see

a wonderful calligraphic
quotation from the Koran

You see the history
of the whole city,

in a sense the whole region,
in a nutshell

NARRATOR:
But deciding which layers
of its history to display

is a battle that continues
on its walls

Stepping onto the battlefield is
researcher Hitoshi Takanezawa

He's on a hunt for Christian
mosaics that were plastered over

when Hagia Sophia was converted
into a mosque

His challenge is how to find
the Byzantine mosaics

without damaging
the Ottoman decorations

Takanezawa's secret weapon is
this electromagnetic scanner

Normally, it's used to find
structural faults

in things like bridges

Nobody has ever used it
to find Jesus

(speaking Japanese)

HITOSHI TAKANEZAWA (translated):
We're developing new equipment
for investigation

It is crucial we find a
technology that can deduce

whether a mosaic exists without
destroying anything

NARRATOR:
Takanezawa and engineer Satoshi
Baba carefully run the scanner

against the wall

What might they find?

A tantalizing taste
of Hagia Sophia

in its full mosaic splendor
is here,

the church of San Vitale
in Ravenna, Italy,

also built during Justinian's
reign nearly 1,500 years ago

BRANHAM:
Byzantine visitors would be
transported

into an entirely different world

And it was through the mosaics
that this happened

They were a vehicle to bring
the visitor into contact

with the divine

NARRATOR:
That divine glow
of Byzantine mosaics

is what makes them
so awe inspiring

And the mystery material that
gives them that glow

is what will help in the search

for Hagia Sophia's
hidden mosaics

Luciana Notturni
and Gabrielle Warr are using

the same materials to make
mosaics today

They begin with glass discs,

carefully breaking them
into smaller pieces,

until they become tiny cubes
called tesserae

Notturni places each tessera
piece by piece

into a design she's drawn
on the mortar

and carefully angles them
to reflect the light

(speaking Italian)

LUCIANA NOTTURNI (translated):
It is believed

that especially
in the Byzantine mosaics,

the positioning of the tesserae
was directly connected

to where the light was coming
from, so where the windows were,

where the main light sources
were

NARRATOR:
And to make that light shimmer,

they add something else
to the mix

It has a thin layer of gold leaf

And the fact that it does have
gold in it

makes it very reflective
and very luminescent

NARRATOR:
The gold tesserae give
the Byzantine mosaics

a heavenly glow

And because gold is metal,

it may be the key to
rediscovering the lost mosaics

in Hagia Sophia

TAKANEZAWA:

NARRATOR:
Takanezawa's scanner sends
electromagnetic signals

below the surface of the plaster

If the waves strike a buried
metal tessera,

they are reflected back,

creating an image of the inside
of the wall

TAKANEZAWA:

NARRATOR:
The scanner is working

It has detected a mosaic circle
beneath the plaster

But Takanezawa isn't searching
just for circles

TAKANEZAWA:

NARRATOR:
The walls of Hagia Sophia are
hiding more than mosaics

They also hold secrets
to its seismic strength

High above the streets
of Istanbul,

a team is repairing a wall

as part of Hagia Sophia's
ongoing restoration

Sonay Sakar is the lead
architect

(speaking Turkish)

SONAY SAKAR (translated):
What we're doing is removing

all the cement from the surface
you see here

Then we'll repair the layer
of bricks we've uncovered

NARRATOR:
Her team must replace crumbling
cement from a restoration

in the 1950s

She's using a more
resilient mortar,

one formulated from the original
recipe... limestone, sand, water

and a secret ingredient:
ground-up bricks

It turns out the best way to
preserve Hagia Sophia

for the future is to use
materials from the past

SAKAR (translated):
The mortar in Hagia Sophia is
certainly more flexible

than modern mortar

So it adapts to the structural
deformations

caused by earthquakes

NARRATOR:
The flexibility of the mortar
is crucial,

but so is how it's applied

SAKAR (translated):
Hagia Sophia differs
from other structures

because the layer of mortar is
thicker than the bricks

NARRATOR:
Modern brick buildings have thin
layers of mortar,

but Hagia Sophia's layers are so
thick they act like cushioning

Hagia Sophia's bricks also play
a role in earthquake protection

CAKMAK:
Here is an original brick
from Hagia Sophia,

and here is a modern brick

As you can see, the original
brick is significantly lighter

than the modern brick

NARRATOR:
Which turns out to be
very important

CAKMAK:
If you make the weight light,

then the building can sway with
the earthquakes,

like a tree in the wind...

Flexible, but strong

NARRATOR:
1,500 years ago,
other architects built

heavy and massive to protect
against earthquakes

Anthemius and Isidorus,
the Greek architects,

did the opposite

They built light and flexible...

The principle of modern
seismic engineering

But will this world treasure
survive into the future?

Eser Cakti and her team are
building a model

of Hagia Sophia's core structure
to investigate

Their arch problem solved, they
move on to their next challenge:

the semi-domes

They create a mortar
that mimics the materials

of the real semi-domes, and
spread it over a wooden mold

We have worked on paper
for a long time

on how to get it right,

how to make it, and then what
would be the thickness,

what would be the material

NARRATOR:
After the mortar dries,
they remove the wooden mold

But as they take off the mold,
suddenly

a crack appears at the top

Cracks at this stage mean the
semi-dome is clearly too weak

for the shake table test

They break apart the semi-dome

to get a closer look
at the mortar

We have four centimeters coming
from that side

and four centimeters coming
from that side

But the failure part
was too thin

It is almost a half-centimeter

NARRATOR:
A problem with the way
the mortar was applied

caused the top of the semi-dome
to be much thinner than planned

CAKTI:
Some shrinkage occurs after
drying of the mortar

We may consider to introduce
some elements to the mortar

so that its strength properties
will improve

NARRATOR:
The team must rebuild
the semi-dome

And they'll need to come up
with a better method

for building the final piece of
their model...

The large central dome...
And that will take some time

In his hunt for hidden
Byzantine mosaics,

Hitoshi Takanezawa is heading
to the uppermost level

of Hagia Sophia,

a thin ledge that runs beneath
the main arches

The building is so huge,
he must narrow down his search

TAKANEZAWA:

NARRATOR:
Because these niches on the
northern wall are filled

with mosaic figures,

Takanezawa believes the southern
wall may have been too

But have the mosaics survived?

To find out, they run the
electromagnetic scanner

along the wall

TAKANEZAWA:

NARRATOR:
The team takes a closer look
at the scan

They find metal
behind the plaster,

but not the gold
Takanezawa is hoping for

TAKANEZAWA (translated):
There are only horizontal lines

It would seem it is not
a mosaic,

but rather a metal structural
support

NARRATOR:
Takanezawa's guess is wrong;

no mosaics have survived
in this niche

The challenge is
that his scanner measures

about two feet at a time,

and Hagia Sophia's surface area
is over 200,000 square feet

To narrow down his search,

Takanezawa has come to
Bellinzona, Switzerland,

to explore the state archives

Inside, archivist Carlo Agliati
shows him an astonishing record

of Hagia Sophia's
Byzantine mosaics

(speaking Italian)

CARLO AGLIATI (translated):
In 1847, the Sultan entrusted

the architect Gaspare Fossati
with the task of restoring

the mosque of Hagia Sophia

NARRATOR:
These drawings were made
by the Fossati brothers,

Swiss architects who were hired
to renovate the aging building,

which was then a mosque,
in the 1840s

The Fossatis began stripping
plaster from the walls

and were astonished
by what they found

(speaking Italian)

(translated):
Fossati's big discovery during
the restoration,

hidden under the plaster,

was definitely these
extraordinary Byzantine mosaics

NARRATOR:
They quickly documented every
image before covering them

with plaster once again

While some of the mosaics
recorded in the drawings

have been uncovered,
others have never been found

One in particular catches
Takanezawa's eye

(speaking Japanese)

(translated):
There is a circular sketch

from the Fossati,

but the exact location is still
the subject of debate

NARRATOR:
The sketch depicts Christ,
framed by a cross in a circle

Near Hagia Sophia,
the church of Chora

contains a strikingly
similar image

found in the crown of a dome

Takanezawa believes the Fossati
sketch depicts a similar mosaic

in a dome in Hagia Sophia

And he has a hunch
where to find it

(speaking Japanese)

(translated):
A very plausible hypothesis is
that there is a large depiction

of the face of Jesus Christ

at the top of Hagia Sophia's
immense dome

NARRATOR:
But there's a problem

TAKANEZAWA (translated):
Currently it's covered by
plaster and by Koranic verses,

but one day, with our scanner,

we would like to discover
this image

This is my dream

NARRATOR:
It's a dream Takanezawa
could realize

because as part of Hagia
Sophia's ongoing restoration,

this enormous scaffold is about
to reach the dome

But if Takanezawa does
find Christ

beneath the Koranic verse,
what should be shown?

It's a question at the heart of
Hagia Sophia's identity

a question with a long history

CAKMAK:
Religiously, it was
a Greek Orthodox church

And during the Fourth Crusade,

it was taken over,
became a Catholic church

When the Muslims came,
they made it into a mosque

Finally it became a museum,

which we thought was a solution
to the problem

But, unfortunately, the Greeks
would like to make it back

into a church

And the Muslims would like to
make it back into a mosque

And the conflict, controversy
continues

NARRATOR:
But whether Hagia Sophia
remains a museum

or is converted back
to a church or mosque

could prove irrelevant
if there is an earthquake

The more pressing question is

will it be converted
into a pile of rubble?

Eser Cakti hopes the shake table
test will provide some answers

The semi-domes are carefully
rebuilt from mortar

But mortar will be too fragile
for the main dome,

which, like the real thing,
will be built from brick

CAKTI:
We came to the conclusion
that having a brick dome

is much easier to construct
and it's more realistic

So dome-wise, I'm confident
with what will happen

But with respect to the
semi-domes, there I have doubts,

because it's much more fragile

NARRATOR:
Before the test, the seven-ton
model must first survive

the move to the shake table

CAKTI:
This is the largest model ever
to be made in our lab

We need to be very careful
that during lift-up

everything should be perfectly
horizontal

Otherwise, we may damage
the model

NARRATOR:
The model is so heavy
it bends the steel plate

that supports it, which puts
pressure on the structure

It settles onto the shake table,
but has it suffered any damage?

As the wooden molds come away,
Cakti looks for cracks

If the model breaks
at this stage,

they will be unable to perform
the earthquake test

and months of work will have
been for nothing

CAKTI:
Okay, there is some, yeah

We have observed some cracks
on the semi-domes

But we don't see them
from outside

These are just interior cracks

NARRATOR:
Cakti believes the cracks
do not compromise

the structural integrity
of the model

So the team moves on,

installing motion sensors in
similar locations as the sensors

in the real Hagia Sophia

CAKTI:
We will be able to compare
the vibrations

that we record during
the shake table test

with those obtained
from the real structure

NARRATOR:
The model is a scaled-down
version

of Hagia Sophia's core
structure... the main dome,

four great arches, four buttress
piers and the two semi-domes

But will the model move
on the shake table

in a similar way as the real
building moves in an earthquake?

Astonishingly, overnight,

the sensors get an unexpected
trial run: a real earthquake

CAKTI:
At about 4:00 a m

we had an earthquake
near Istanbul

Its magnitude was 3 6

So, by pure chance,

we have now recordings
of that earthquake

recorded on the model

And we have the same earthquake
recorded by our instruments

in Hagia Sophia

NARRATOR:
The parallel recordings verify
that the sensors on the model

and in the real building
are reacting in a similar way

Now it's time to see
how the model will react

to a more powerful quake

(speaking Turkish)

They calibrate the shake table
to simulate the impact

of the devastating '99
earthquake, magnitude 7 4

The duration of the test
is scaled down

to match the size of the model,
about three seconds

The sensors capture every twist
and turn

The model seems to have taken
the impact without damage

But what everyone really wants
to know is how will it stand up

to an even stronger earthquake?

To find out, the team must push
the power of the shake table

beyond anything
they've tried before

The simulated quake
is measured in g's...

Its gravitational force

We are increasing the amplitude
of our earthquake one more step

so that now we aim 2 2 g

You said two was the maximum

Now we are going more than two?

If we can do it,
we'll go for 2 4

Perfect

NARRATOR:
They hit the model
with a simulated earthquake

stronger than any in
Istanbul's recorded history

Cakti checks out the damage

I see one new crack in this arch

But surprisingly, there is
nothing new with the semi-domes

We were afraid about them

But they are as they
have been before

NARRATOR:
The Hagia Sophia model
has survived

two enormous earthquakes in
quick succession,

with minimal damage

But the team isn't done yet

We have passed the known
capacity of our shake table

And then it appears
the mechanics

have allowed us to go further

NARRATOR:
Can the shake table push the
model to the point of collapse?

They hit it with everything
they've got

At this stage, the model has
been hit by the equivalent

of a major earthquake every day
for a week

And although it teeters
on the edge of collapse,

it still stands

There are two vulnerable
parts... the semi-domes

and then the arches

It is just a matter of time to
see which one will go first

NARRATOR:
With everyone's eyes on
the semi-domes and arches,

nobody anticipates
what happens next

The great dome comes
crashing down

I am a little bit surprised now

because I would have expected
the main arch to go,

and then instead of the main
arches, the main dome went

NARRATOR:
The slow-motion replay reveals
that the semi-domes separated

from the structure

and with the main arches
damaged,

support for the dome was
severely compromised

KORHAN ORAL:
My masterpiece is collapsed now

But for scientific observation,
I can accept it

CAKTI:
Now we have come to its end

But, at the same time, we know
that we have lots of things

to do in terms of data analysis
and interpretation

This is a little bit
frightening,

but it needs to be done

NARRATOR:
It is too early to draw
any firm conclusions

But the model going 15 rounds

against the most powerful
simulated earthquakes

the shake table could produce

explains Hagia Sophia's
supposedly miraculous survival

CAKTI:
If there is a miracle,
it is in its design

It was constructed to survive

The balances between its
structural elements

appear to create a dance

The domes, arches, semi-domes,
buttress piers,

they behave in harmony

NARRATOR:
Though the model lies in ruins,

Cakti believes the data captured
in this experiment

will provide new insights

into Hagia Sophia's
structural strength

and how it can be preserved
for the future

OUSTERHOUT:
Scientists have spent decades

trying to analyze the structural
system of Hagia Sophia

But when you go inside
Hagia Sophia today,

you don't see structure

We're not meant to understand
how the great dome is supported

We see only the weightless
quality of the building

That was what was most important

We understand the interior
of the building

as an experience that's
completely different

from anything else on earth

NARRATOR:
After nearly 1,500 years,

Hagia Sophia continues to
astonish modern builders

with its ancient secrets of
seismic engineering,

and for its resilience not
only as a structure,

but also as a symbol
of the great civilizations

that have adopted it

SAKAR (translated):
We don't think of Hagia Sophia
based on the meanings

other people assign to it

Hagia Sophia has an identity
of its own

It is a monumental building;
it is a special building

Our goal is to pass it down
to the next generations

NARRATOR:
Hagia Sophia will have to endure
many more shifts in the ground

that lies beneath it,

and the cultures to which
it is entrusted

Hopefully its majestic beauty
and innovative design

will inspire people of all
religions and cultures

to protect it for generations
to come