Original subtitles

[dramatic music]

ERIC GELLER (VOICEOVER): Walk anywhere

in the city of Istanbul, and you're

walking on top of the past.

Dig anywhere beneath the streets,

and you'll uncover thousands of years of hidden history.

Most historic cities have been extensively excavated,

but in Istanbul archeologists have just barely scratched

the surface.

On our quest to peel back the layers of the city's

buried past, there's no telling what we'll find.

This is incredible.

This is very impressive.

Pretty amazing.

We're underground in Istanbul but in a boat.

ERIC GELLER (VOICEOVER): There is an entire world

beneath our feet, layers of history

left behind by the Romans, Byzantines, and Ottomans.

We'll bring the cities of these fallen civilizations

back to life, and empires will rise from the ashes once again.

We're peeling back the layers of time

to uncover the cities of the underworld, Istanbul.

[dramatic music]

It's been called Byzantium, New Rome, Constantinople.

This strategic peninsula sits with the Marmara sea

on one side and the Bosphorus Strait on the other.

It's the only city in the world that straddles two continents.

This prime location made it the perfect spot for empires

to rise, fall, and rise again.

I'm Eric Geller.

I'm in Istanbul, Turkey, and for centuries, this

was the most powerful city in the world.

But when you're on top, the only place to go

is down, and down is where these empires went.

If you dig anywhere, you'll find evidence of the fallen

civilizations.

There are cisterns, and libraries, dungeon,

hidden tunnels.

There are entire cities buried beneath our feet.

Now, we can't shut down today's modern day city to excavate,

but there are other ways to get underground.

ERIC GELLER (VOICEOVER): Today, Istanbul

is part of the Democratic Republic of modern Turkey,

and the city's 11 million inhabitants make up

a melting pot of the cultures these fallen empires have left

behind.

Everywhere you look the past and the present collide.

Taxis whiz by the 1,500-year-old Byzantine church, Ayasofya.

Couples stroll by 1,000-year-old Roman city walls,

and tourists take pictures of the almost 400-year-old Ottoman

Blue Mosque.

In most cities around the world, this would be it,

but in Istanbul, it's only the beginning.

We'll peel back the layers of time,

whisk away today's houses, busy streets, and modern bazaars

to find a hidden history like no other city in the world.

I'm not talking about a catacomb or a tunnel or two.

We're walking on top of entire cities stacked like bricks,

each layer of history buried deeper than the next.

The city began in the seventh century BC

as a small Greek fishing village called Byzantium.

200 years later, the village became a part of the vast Roman

Empire, and in 330 AD it was renamed Constantinople

after emperor Constantine moved his entire capital east.

The Eastern Roman Empire, later known as the Byzantine Empire,

was born.

For more than 1,000 years the Byzantines flourished here.

Then in 1453 Constantinople was conquered by the Ottomans,

becoming Istanbul.

Almost 500 years after that, the modern Turkish Republic

was born.

For 27 consecutive centuries, these civilizations,

the Greeks, the Romans, and the Turks,

built palaces, stadiums, bathhouses, roads, each one

trying to outdo the one before.

Each time the city was destroyed, the next generation

simply rebuilt atop the ruins of the past,

adding their own layer and in some cases,

raising the ground level by more than 40 feet.

But how is this possible?

How does an Ottoman mosque literally

sit on top of a lost Roman palace or an apartment

building not cave in to the ancient Roman system below?

My quest for answers begins almost 1,700 years ago,

when Istanbul was the new capital of the Roman Empire.

For centuries, this city's prime location

made it the most desirable spot in the world.

The Romans knew this, and they acted quickly

to defend their new capital.

They built impenetrable city walls.

They chained off their harbors, and perhaps most ingeniously,

they found a way to protect their greatest resource,

drinking water.

And it all started right here.

ERIC GELLER (VOICEOVER): The aqueduct

was one of the Roman Empire's greatest engineering feats.

Beginning in the fourth century, Constantinople's water

began its journey 12 miles from the city center

in the forest of Belgrade.

Powered entirely by gravity, the precise slope of the aqueduct's

construction ingeniously carried large amounts of water

across uneven ground until it was safely inside the city

walls.

The water was then diverted to one of five open-air cisterns.

Here it would purify itself, depositing

mineral and organic matters, while still keeping

its pressure.

Next, the water made its way into the many subterranean

tunnels snaking beneath the city streets.

Its final destination was one of the thousands

of underground cisterns.

Here it was stored until a citizen of Constantinople

decided to pump water from the fountain up above.

I met up with historical guide Bora Sertbas

in Sultanahmet Square.

- Bora. - Hi, Eric.

How are you?

ERIC GELLER (VOICEOVER): He was going

to show me the largest underground cistern

in the city.

Many believed it was from here that the emperor himself got

his water.

In a minute you won't believe your eyes

what you will see down here.

This is a totally different life than what you've seen above.

ERIC GELLER (VOICEOVER): It's called the Basilica Cistern,

but the Turks call it Yerebatan Sarnici.

Surete or sunken palace.

And that's exactly what it looked like.

Oh, this is amazing.

The Basilica Cistern.

ERIC GELLER: This is-- look at the size of this place.

BORA SERTBAS: This is a huge place.

You would have no idea coming in off of the square.

Yeah.

I mean, there's restaurants right there.

About here.

There's a park right here.

A police station, everything.

This is massive.

And we are going to see about over 100,000 square feet

of an area here.

This is the biggest underground cisterns ever built

by the Romans in this city.

ERIC GELLER (VOICEOVER): Emperor Justinian

was responsible for building the cistern in the sixth century.

He also built the nearby Ayasofya

and was the emperor under which paganism died

and Christianity flourished.

During his 43-year rule, he was ambitiously

able to reclaim the Western Empire, reform Roman law,

and rebuild much of Constantinople.

Today, the Basilica Cistern is one

of the largest Roman structures left in the world.

It's 459 feet long and 229 feet wide.

The roof is supported by 336 marble pillars spaced

approximately 15 feet apart.

The cistern was the key to the survival of the empire.

Since the city was constantly under siege,

the aqueducts, which acted as natural bridges into the city,

had to be broken to prevent entry.

The water stored in the system helped sustain the residents

of Constantinople for months at a time.

After the conquest, 1453, when the Ottomans

came into the city, nobody gave them a tour, OK,

so they didn't know where is what.

For that reason, the underground cisterns

were not discovered for a long time.

ERIC GELLER (VOICEOVER): But even after they were

discovered, the Ottomans didn't feel as vulnerable to attack

as the Byzantines, so they didn't rely on them as much.

In addition, the Ottomans' cultural preference

for running water, not still, helped

add to the cistern's downfall.

In the Turkish culture, still water's considered dirty.

When it runs, it's clean water, and this is what we use.

ERIC GELLER (VOICEOVER): So the basilica system

was forgotten beneath the streets

until 1544, when a Frenchman named Pierre Gilles became

suspicious of the endless supplies of water and fish

the locals were pulling out of their basements.

Gilles is credited with rediscovering the Basilica

Cistern after being invited to fish beneath the basement

of an old Ottoman home.

[dramatic music]

Today the Basilica Cistern sits more than 25 feet

underneath the modern city.

For almost three city blocks, anything you see,

trains, restaurants, hotels, even the police station

is supported by the sixth century sister.

The decorative marble columns credited with holding up

today's city were once immersed in water

and were never meant to be seen.

They were just the recycled trash

of Byzantine construction, leftovers

taken from nearby temples or monuments.

ERIC GELLER: How come it doesn't fall down?

How come, you know, the police station isn't right there?

How come this whole city hasn't caved in?

[laughs] That's a good question.

Now, at this point, we should remember the very important

thing.

City is built on seven principal hills, like Rome.

When they had a valley, they erect columns in there,

put in the Roman arch, cover it.

With one stone you shoot two birds.

You can have a water storage underneath,

and you have a flat surface now above.

ERIC GELLER (VOICEOVER): Approximately 1,500 years

and 25 major earthquakes later, these columns were still

supporting the cistern and the city above,

but they were also meant to hide some of its secrets.

ERIC GELLER: So who is this fine person?

BORA SERTBAS: This is Medusa from the Greek mythology.

Why is Medusa here?

Is there some symbolic reason for that?

That's a very good question, actually.

One explanation is, since everything is recycled material

here, this is what they needed.

They needed this size of a stone.

They put it underneath, and they elevated to the height

they wish.

ERIC GELLER (VOICEOVER): But in Istanbul there are always

other reasons.

BORA SERTBAS: Another explanation is--

532 is the year.

The most Christian Emperor, Justinian,

is building across the street the Hagia Sophia,

the biggest church ever built in the Roman period.

He was a very religious person, and by burying Medusa,

a pagan symbol, under the column on the side and there upside,

drowning her inside the water, he

was giving a message that the pagan beliefs is helpless even

to itself.

So not only are they storing water here,

but they're hiding the past.

They're burying paganism at the bottom of the cistern.

I couldn't say it better.

ERIC GELLER (VOICEOVER): Istanbul has been called

the City of Cistern, and while the Basilica Cistern is

the biggest, it's just one of the hundreds

of gaping ancient holes forgotten

beneath the modern city streets.

I would say even some people wouldn't know they have cistern

under their houses, and they're sitting

on a heritage of 1,500 years old without even knowing it.

[traditional music]

ERIC GELLER (VOICEOVER): Nakkas is located in the old quarter

of the city and specializes in high-end Turkish carpets,

pottery, and jewelry, but the real treasure

is hidden beneath the store.

Owner Cengis Korkmaz has agreed to take me down.

Yeah, you can definitely feel the humidity.

This is our cistern area.

Amazing, amazing.

Isn't that beautiful?

ERIC GELLER: It's amazing.

CENGIS KORKMAS: It's an incredible place.

ERIC GELLER (VOICEOVER): A cistern of this size

would normally require only about eight columns

for support, but this one has 18,

indicating an important palace building might have been on top

of it.

Today history is repeating itself.

ERIC GELLER: You've got a massive store above it, 20,000

square feet roughly. CENGIS KORKMAS: Yes.

ERIC GELLER: What kind of considerations

do you have to do to preserve this cistern?

Actually, in the process of building on top of the cistern,

we really thought very carefully.

We said, we have to keep this place in authentic size

and originality, so with did a special kind of construction.

ERIC GELLER (VOICEOVER): Nakkas was designed by an engineer who

came up with a groundbreaking way to build the new

1,000-square-foot building above while protecting the Roman

cistern below.

Instead of using reinforced concrete beams,

they used steel.

That's 10% to 15% less pressure on the structure below

and 30% less than the older buildings

that once unknowingly sat on top of the system.

CENGIS KORKMAS: We built more than beams

than we needed to distribute the weight of the building above so

not to give any pressure to the system.

So the main thing is that lighter weight, more columns

to support it, steel columns?

Exactly.

ERIC GELLER (VOICEOVER): 30 steel beams

instead of the required 20 we're used to distribute the weight.

Next, engineers actually reoriented the building

and angled it so it didn't sit directly on the cistern.

This way, only eight of the 30 beams

come in contact with the cistern.

The entire project cost $2.5 million.

Without the cistern, it would cost half that.

There's a lot of things underground of Istanbul,

and I believe, as much as we have on ground,

we have much more than that underground of Istanbul.

But they're all waiting to be discovered.

[cheering]

It's Saturday night in Istanbul, and this is the place to be.

But when the Romans were here, they built a stadium

twice this size.

Now imagine a deadly chariot races

circling the field, the emperor and his family

in the royal box, and about 100,000 screaming people,

just like these.

Now, this great hippodrome-- it still exists.

It's just about 15 feet beneath the city streets.

[traditional music]

ERIC GELLER (VOICEOVER): But how can an ancient race

track twice the size of Istanbul's biggest soccer

stadium just disappear beneath the ground, and how could

I get under there to see it?

[dramatic music]

Hi, Eric.

ERIC GELLER (VOICEOVER): I met with Cimen Filiz Pasa,

an historic guide in the busy tourist square of Sultanahmet

in the old quarter of the city.

Today's modern city has spread far beyond the original Roman

city walls and across the Bosphorus Strait into Asia,

but remnants of the old city still remain beneath our feet.

[dramatic music]

In 306 AD, Constantine was named emperor of Rome,

dubbed Constantine the Great by Christian historians

for legalizing Christianity during these pagan times.

He also successfully united the vast Roman Empire

under one emperor.

As his empire grew, Rome became further away from the empire's

eastern expansion, so in 324 AD, Constantine

chose to move his capital to a strategic but provincial city

called Byzantium, later Constantinople.

Not long after the move the Roman empire's

western provinces, including Rome, fell to the barbarians.

In 330 AD, the Roman Empire, with Constantinople

as its capital, became known as the Eastern Roman Empire, later

called the Byzantine Empire.

Constantine's decision to relocate

had changed the course of history,

making Constantinople the most powerful place on Earth.

The palace, the Hippodrome, and the church

Ayasofya where the three most important buildings

of the empire.

This trifecta was once located in the square where

we were walking.

Today, Ayasofya is the only building of the three

still standing above the ground.

The original Hippodrome was built in 203 AD

by the Roman emperor Septimius Severus, but in 324 AD,

Emperor Constantine began to add his own layer by expanding

the original structure to rival Circus Maximus in Rome.

He added more seats, enough to fit 100,000

cheering spectators, and extended the U-shaped track

to over 1300 feet long and approximately 250 feet wide,

an arena the size of five and a half football fields.

He decorated the center spina or median

with monuments brought in from regions throughout the empire.

These monuments were a reflection of Rome's power

but were also used to block the view of the spectators

on purpose.

They added to the suspense of the spectators

as the chariots disappeared and reappeared

from behind the spina as they rounded

the deadly U-shaped turns.

But the Hippodrome wasn't just for entertainment.

It was also a place for citizens to confront their emperor,

often resulting in bloody riots.

After a chariot race and 532 AD, angry protesters

began a revolt against Emperor Justinian's rule.

After five days of protest, between 30,000 to 50,000

rioters were slaughtered.

This infamous event was called the Nika revolt,

and the bodies of its victims are

rumored to be buried in the bowels of the Hippodrome.

Byzantine bones, spectator seats.

There were no bulldozers to clear away the remains,

so no one knows for sure what they'd find layered

beneath today's pavement.

But three surviving monuments from the Hippodrome's spina

act as the perfect gauge for determining how much the ground

level has changed in almost 1,700 years.

CIMEN FILIZ PASA: If you go look down,

you can see the original level of this spina.

I'm sure.

Right, right, right.

And it is like almost 15 feet down.

ERIC GELLER (VOICEOVER): But Cimen told me,

before I tried to go down, I should go up

to really understand the evolution of the Hippodrome.

I was granted special permission to climb one of the six

minarets or towers of the famous Blue Mosque, the highest

vantage point in the old city.

This iconic mosque took the Ottomans seven years to build

and was completed in 1616.

It is believed to sit directly on top

of the ruined western stands of the Hippodrome

and the remains of the emperor's royal box.

ERIC GELLER: We're climbing 135 steps, a little wider here.

I never thought I'd be inside a minaret, a little darkness

here.

This is incredible, definitely worth the climb.

So you can roughly see what would have been

the outlines of the Hippodrome.

From about that green fountain where the road follows around

was this massive racecourse.

It goes around the obelisks, and right around that building,

all the way around here you would have seen chariot races

and all the festivities that went on in the Hippodrome.

This must have been a massive place.

[traditional music]

ERIC GELLER (VOICEOVER): But the transition from horses rounding

the tracks to taxis 15 feet above didn't happen overnight.

The tradition of the Hippodrome came from the pagan Greeks,

and in a city full of both Christian and Muslim

influences, it was no wonder it ended up

buried beneath the ground.

This Hippodrome, for 1,000 years,

center, heart of the Roman Empire.

It was important for Byzantium also,

but the importance changed because in paganism you

live in this arc, in this life, but in Christianity, this

is your suffering place.

If you are going to be a good believer,

you don't have time to joy, for entertaining.

ERIC GELLER (VOICEOVER): The pious Byzantines

may have had no time for fun at the Hippodrome,

but it was another religious group who silenced the stands

for good.

In 1204, the fourth crusades breached the city walls,

and the richest Christian city in the world

was pillaged beyond recognition.

The crusaders destroyed almost everything,

including the Hippodrome.

They looted four fifth-century bronze horses on display

in the Hippodrome and took them back to Venice.

For centuries, they were on display at the famous St.

Mark's Cathedral.

When the Ottomans conquered Istanbul in 1453,

the great Hippodrome was in ruins.

CIMEN FILIZ PASA: The Ottoman Empire also paid importance

to this place.

This was the center of the city.

That's why they built all their beautiful building around here.

ERIC GELLER (VOICEOVER): Much of the elevated ground level

we see today came about when dirt and debris from building

the Blue Mosque was dumped to the side,

right on top of the old race track.

Construction of other Ottoman buildings in the square

did the same.

So beneath the ground of the square

I find the race track of the Hippodrome,

but just a few minutes walk down a natural valley,

Cimen was about to show me the only structural part

of the Hippodrome still standing.

It's called the sphendone.

You see, this is the sphendone .

This is the outer wall of the Hippodrome.

It has a curve, and when we have a car and a higher platform,

we call it sphendone.

[dramatic music]

ERIC GELLER (VOICEOVER): Today, on top of the sphendone

sits a more recent layer of the past, Sultanahmet Technical

High School.

This is a third-century wall that

was part of the Hippodrome, and right now its construction

is so solid that it's holding up the school, pretty good

Roman engineering.

The sphendone was holding up the high school and much

of Sultanahmet Square, and it was

all that was stopping me from getting

beneath the ancient Hippodrome.

ERIC GELLER (VOICEOVER): Most locals never think twice

about the inconspicuous third-century wall

in the middle of Istanbul's Sultanahmet Square.

But beyond it lies the remains of the ancient Roman

100,000-seat Hippodrome.

The area has never been fully excavated by archeologists,

but I was determined to see what remained of its underworld.

Based on the Circus Maximus in Rome,

the Hippodrome was built into a natural valley

that slopes southward towards the sea.

Engineers first closed off the south end of the valley

with a U-shaped wall called the sphendone.

It rose over 130 feet high and linked up with the stands

while the racetrack sat below on the valley floor.

While the track was flat, the ground

slopes down towards the sphendone,

creating a cavernous underbelly or backstage,

starting where the track ends and the sphendone begins.

This underbelly was rumored to be intact,

and we'd been granted special permission by the antiquities

authorities to get inside.

Even archeologists have trouble gaining access.

A little difficulty opening the gates to the Hippodrome.

[inaudible]

What do you think?

We have some friends down here.

We got some, like, little dung beetles or something.

[suspenseful music]

Whoa, whoa, whoa.

What are we seeing here?

It looks like, actually, like it sort of naturally

filled in on itself, like maybe the roof gave in.

I can't tell if this was filled in or not.

It's hard to get a sense.

But this case goes back further, but I

don't think we're going to be able to get back there,

at least through this way.

ERIC GELLER (VOICEOVER): Off the circular corridor,

I could see about six rooms, and inside each room

was a caved-in entrance to another tunnel.

Could these lead to the racetrack of the Hippodrome?

ERIC GELLER: So this room and all these other chambers

like this would have been behind the scenes.

It would have been like in NASCAR, a pit stop, right?

The race car blows a tire.

It needs more fuel.

They might have come right in here.

They could have had chariot supplies, wheels, water,

anything you need, and 100,000 screaming people

were standing right out there.

I see steps.

Oh, wow.

Can you hear that?

Can we explore down here?

I hear something scampering around.

CIMEN FILIZ PASA: Be careful, Eric.

I'm trying to be careful here.

It looks like it's a good 30, 40 feet up from here,

and the masonry and stonework looks impeccable.

And it'd have to be if it stood up for, oh, let's say, 1,500,

1,600 years.

It looks like I can't take another step down because it

looks like it's-- it's flooded out down here.

Yeah, this doesn't look like it's probably

the end of the road for us.

ERIC GELLER (VOICEOVER): The water

was preventing me from exploring the Hippodrome any further,

or was it?

Hasan bey!

It's nice to meet you, Hasan.

Hasan Oral is an urban cave explorer

who has navigated secret tunnels and waterways deep

beneath the entire city.

Take some of the boats.

OK.

So we've got simply a rubber raft in their, rubber boat?

Yes, yep.

OK.

Have you ever been in here before?

Have you been?

No, this is the first time.

So you don't know what you're going to find, do you?

No.

Down is the [inaudible].

One.

Gotcha, gotcha.

OK, now let's go inside.

OK.

I'm just going to grab whatever I can.

ERIC GELLER (VOICEOVER): Would we find the tunnels

where the horses galloped into the Hippodrome

or the passageways that led to the emperor's royal box?

ERIC GELLER: Yeah, I think there's a little bit of a leak.

Could be.

So we're going to get stranded somewhere in the Hippodrome,

and they'll find us 1,000 years later.

OK.

Go now.

What do you think?

Now I go in on my knees, I'm guessing.

Yes, yes.

On your knees is the best.

Yeah.

OK.

OK.

Can I have a paddle?

Here's a paddle for you.

It's pretty amazing.

We're underground in Istanbul but in a boat,

and we're paddling through the Hippodrome.

And clearly you're getting run-off from pollution

from the streets.

It smells like feces.

I mean, I don't know what's down here,

but it's not very pleasant.

But this used to be the center of the city.

I mean, you hate to say it, but this very well

could have been a toilet for the Hippodrome, right?

This could be ancient [bleep] that floating in this water.

It seems like about every, what, 20 or 30 feet

we find a new chamber.

There could have been supplies here, storage for chariot's.

I mean, it's big enough to be a stable.

There could have very well been horses in here.

This could have been where the athletes prepared

or the circus entertainment.

It looks like there's some debris over here.

I can't even make this out over in the corner.

It is concrete.

It is concrete there.

We had hit another layer of history.

The wall was clearly not Roman or Byzantine.

It was most likely the remains of a late Ottoman wall.

Hasan says the Ottomans had turned the sphendone

into a cistern for water storage.

The walls were covered in concrete,

and based on the water we had just paddled through,

the cistern was still doing its job.

So this is our way, but we've got to see what's behind it.

We've got to keep going, right?

Yeah, so let's climb it.

All right, let us climb.

[dramatic music]

OK.

All right, let's do it.

All right, we're getting our first look.

I'll tell you what I see here.

This is exactly a flat face.

It's a smooth face.

We're dammed off right here, and it's a smooth face.

And we don't have the equipment to get down.

You can see more water down there in this tunnel,

and maybe this tunnel right here would lead directly

into the Hippodrome.

And I'm sorry to say I'm not going to be able to see it.

So this is the end of the road for us,

but Rome wasn't built in a day.

And we're not going to discover everything about Istanbul

and its underworld in one day either.

And Hasan, you're going to be the one who gets to find out

what's over there, huh?

Yes, I think that we will come with more people and some more

equipment that we have a look what's there.

[upbeat music]

Today we know this city as Istanbul,

but almost 1,700 years ago this was Constantinople,

the very spot that Emperor Constantine hand-picked to be

the new capital of the Roman Empire.

Constantine wanted his capital to be bigger and better

than Rome.

He started by building a palace that would become

the envy of the world.

So where is this grand palace now?

[dramatic music]

ERIC GELLER (VOICEOVER): The palatial complex Constantine

built here when he relocated his capital was called the Great

Palace and stretched for approximately

860,000 square feet.

That's larger than 15 football fields.

The palace compound began at the Sea of Marmara

and continued all the way to the Hippodrome.

Off limits to the public, it was like a small city

for the emperor and his royal court.

The grounds housed state buildings, throne rooms,

churches, libraries, thermal baths, fountains,

and ornate courtyards.

Its bronze gates, roaring mechanical lions,

and mosaic tile sidewalks made it one of the wonders

of the ancient world.

But towards the end of the Byzantine Empire,

in a much debated move the royal family

left this grandeur for a smaller palace further inland.

No one is exactly sure why, but this decision

was the start of the decline of Constantine's famous Great

Palace.

When the Fourth Crusade sacked the city in 1204,

the crusaders are said to have lived

in the remains of the palace they helped to destroy

and even stored their stolen loot there.

The Ottomans conquered in 1453 and began to rebuild the area

to suit their needs, recycling materials left behind.

Soon walls of the palace became walls of Ottoman homes.

Byzantine stones helped build new mosques.

After 470 years of Ottoman rule, the great palace slowly

had disappeared beneath the ground

and was all but forgotten until 1912,

when a fire raged through Sultanahmet Square,

destroying hundreds of homes.

When the debris was cleared away,

Constantine's Great Palace rose from the ashes.

The lost seat of Rome was found, and I

was about to see it for myself.

The fire had helped to unearth a fourth-century palace courtyard

and one of the best examples of mosaic artwork in the world,

artwork commissioned by Emperor Justinian

200 years after Constantine first

built this imperial palace.

The mosaics had been hidden by homes for centuries.

ERIC GELLER: So essentially this grand mosaic

is a sidewalk for emperors.

They would have strolled onto the Hippodrome, perhaps,

or another part of their palace, and you

can see how gorgeous this is, how grand the palace must have

been.

It's not hard to imagine that Emperor Justinian himself

followed the same path that I am, of course, on the mosaic.

ERIC GELLER (VOICEOVER): The mosaics

were part of a royal peristyle or enclosed courtyard lined

with columns.

The courtyard was part of the massive complex

of the great palace.

Today I could only see 2,690 square feet, only one eighth

of the entire size of the courtyard,

but 1,500 years ago, the mosaics would

continue for approximately 20,000 square feet.

That's 75 to 80 million handcrafted mosaic sidewalk

pieces.

I met up with archeologist Ferudun Ozg m s to find out

where the rest of the palace was hiding.

Hello, sir.

Very nice to meet you.

Thank you for your time.

ERIC GELLER (VOICEOVER): He grew up in the old city

and was playing in subterranean tunnels

and the substructures of the great palace before he

or anyone knew what they were.

This brick right here, right, if I remove this brick

and keep digging, what am I going to find?

The ruins of the great palace right underneath that?

ERIC GELLER (VOICEOVER): He's taking me beneath the streets

to a part of the great palace that has never been excavated

and few know exist.

Asia Minor Carpet Shop doesn't look much different

than all the other carpet shops on the block,

but beneath its courtyard store owners came across an entrance.

One wheelbarrow at a time, they began removing the dirt

until they had exposed five vaulted chambers believed

to be part of the substructure of Constantine's lost Great

Palace.

This is very impressive.

ERIC GELLER (VOICEOVER): We were in the substructure or basement

of the great palace.

The throne room, where Constantine greeted his guests,

was believed to have once stood just above our heads.

The Byzantines are rumored to have kept wild animals down

here.

The crusaders may have walked through these very rooms.

Later, the Ottomans are said to have used these rooms

as prisons.

So I see you searching around this room somewhat frantically,

but it's as if you're putting together

the pieces of a puzzle.

And here?

ERIC GELLER (VOICEOVER): It was actually an Ottoman wall

blocking off a tunnel once supported by a Roman arch

later reinforced by a Byzantine arch.

That's three empires all making use

of the same space, 1,700 years of layered history right here.

So it looks like just beyond this mound there's another arch

that-- - Yes.

--leads to another room.

And all of these things very well

could have led from the palace to Ayasofya to the Hippodrome

because we're not that far away from the Hippodrome.

So this could have led to the Hippodrome.

Yes, it could, yeah.

ERIC GELLER (VOICEOVER): That meant almost every building

or shop for 30 blocks sat on top of a part of the substructure

of the palace.

There could be escape routes underneath the nearby hotel.

A modern restaurant could be on top of the pathways that

let exotic animals to the Hippodrome,

and a taxi might be driving over one

of the palaces lost libraries right now.

It looks like a built-in chamber.

There's another layer below there?

This could have been a tomb?

ERIC GELLER (VOICEOVER): Without proper study,

Ferudun says there's no way of telling if this is really

a tomb, but evidence of one just added to the mystery

of this city's subterranean.

[traditional music]

ERIC GELLER (VOICEOVER): After almost 300 years of Roman,

1,000 years of Byzantine, and 500 years of Ottoman rule,

Istanbul's underground is like a museum that has acquired

a collection of exquisite cisterns, priceless mosaics,

and secret palatial rooms.

But these treasures share the soil with a more sinister side

of Istanbul's past.

Three months ago, just across town in the quiet neighborhood

of Balat, one of the Byzantine Empire's most brutal

and notorious dungeons was found.

Guide Ali Pasa and chief archeologist Sirin Akinci

agreed to take me down into the 12th-century Anemas Dungeon--

Watch you steps.

Watch your hat as well.

ERIC GELLER (VOICEOVER): --where the most common form of torture

was to burn out a prisoner's eyes.

[dramatic music]

So if you look up, you get a good sense of how far down we

are, and maybe from the bottom down

it's probably, what, about 60 feet, 80 feet, something

like that?

I mean, you get a sense of how many rooms,

at least just from off this view.

There's one, two, three, four, five, six sections

that I can see just right here.

So this looks like quite a maze here.

ERIC GELLER (VOICEOVER): This nearly 1,000-year-old prison

started off as an annex for the nearby Byzantine Tekfur Palace,

but unlike the early Romans or Ottomans,

whose rulers all shared a bloodline,

anyone could become the next emperor of the Byzantines.

Over the next 350 years, plots to kill the emperor

were so common he needed a place large enough

and a punishment severe enough to hold

on to his position of power.

ALI PASA: So what happens to you--

they start torturing you.

They blind you, and they cut your tongue.

They may pierce your ear drum.

They would even castrate you.

So they may keep you forever here until you're nobody,

nothing, just kind of a creature that cannot speak.

Not a pretty place to be.

No, not really.

ERIC GELLER (VOICEOVER): Just three months ago, this dungeon

was full of dirt and debris.

Locals had heard rumors of it, but no one

could have imagined something so huge

was buried underneath their neighborhood

and directly beneath this 16th-century mosque.

The dungeon below is shaped like a backbone.

The long corridor that becomes wider towards the end

resembles the spine, and the 12 vaulted chambers branching off

on each side resemble the vertebrae.

It's believed that the subterranean dungeon was three

stories high, ranging from 60 to 80 feet in height,

with wood planks that have since disintegrated separating

the floors but not the torturous cries.

Rooms where approximately 10 feet wide,

and between 30 to 40 feet long.

12 Byzantine arches act as support

for this underground structure, as does the rocky hill

the dungeon was built into.

Sirin Akinci has only begun to clear out

one side of the dungeon.

An identical wing is believed to be buried just beside this one.

[dramatic music]

But what else is buried beneath Istanbul?

A worsening traffic problem became the catalyst

to find out.

How are you, sir?

Thank you very much.

Murat Ozt rk is overseeing one of the world's most ambitious

public transportation projects.

The $2.6 billion Marmara project will add over

200 miles of tunnels to Istanbul's already crowded

underground.

The end result will be the third largest metro system in Europe,

and it's expected to ease the traffic congestion of the city

by 40%.

Ozt rk brings me down almost 100 feet,

the equivalent of a 10-story building,

deep into the bowels of Istanbul's infamous

underground.

INTERPRETER: We're building a world in which seven or eight

million people at the same time can move around

beneath the ground of Istanbul.

ERIC GELLER (VOICEOVER): But how do they dig without disturbing

the past?

The answer is by digging deep.

Some of the richest cultural layers of the city

were left behind by the Byzantines and Ottomans

and are found between 6 and 65 feet below street level,

so the metro has to dig even deeper, to 75 feet or more.

In addition, a team of engineers use sonar

to determine where artifacts were buried,

and the path of the metro was mapped out accordingly.

INTERPRETER: But in a city like Istanbul,

you can meet with something else, something

different at every 10 meters below the surface,

so we should be prepared to face it, to find it.

And so if you do run into an antiquity,

do you just change directions?

MURAT OZT RK: [speaking turkish]

INTERPRETER: If what we face is too massive,

we might have to change our direction as well.

ERIC GELLER (VOICEOVER): To avoid

this, teams of up to 80 archeologists

work quickly to safely remove whatever they

can from the path of the metro.

When you talk about Istanbul, archeologists are our partners.

Archeologists are the biggest supporters of our construction

sites.

ERIC GELLER (VOICEOVER): At the Yenicapi metro dig site

a few miles away, official digging hasn't begun,

but archeologists are working against the clock

to remove one of the dig's greatest finds

from the path of the metro.

It's a find that was truly unexpected.

Dr. Cemal Pulak from Texas A&M University

was brought in to help.

And the main reason why I'm here

is in one of their soundings, they

stumbled on two shipwrecks, and I came here about two months

ago.

And since then, they've stumbled on three more,

and maybe tomorrow we'll have another half a dozen.

ERIC GELLER (VOICEOVER): Dr. Pulak

is an underwater archeologist specializing

in ancient shipwrecks, and while today Yenikapi

is over a quarter-mile away from the sea,

it was once part of a massive Byzantine harbor.

[suspenseful music]

We go 13 feet down and over 1,000 years back

into Byzantine history to the 11th century sea level.

CEMAL PULAK: We're standing at the bottom of the lake 10th,

early 11th century Byzantine Harbor floor.

OK, so 1,000 years ago we'd be swimming right now?

That's right.

ERIC GELLER (VOICEOVER): Cemal says a storm caused

this 11th century merchant ship to sink

to the bottom of the harbor.

The large port side in front of us lodged into the harbor floor

and was immediately covered by a protective layer of sand.

CEMAL PULAK: As soon as the ship sank, it was covered over,

and even the people who lost the ship must have looked for it.

And they lost it.

But then over time, of course, the harbor silted in,

and it became marshland.

Then, of course, once the area dried up,

it was used as an orchard or gardens,

and then eventually the city took over from the 16th century

onward.

And then we have continuous habitation

on top of the sea to the 21st century,

and people living above it had no idea

that this was once the sea and there are shipwrecks

laying below them.

And as a ship that's found right in the middle of the city just

by chance only because they were constructing the metro,

we have here before us perhaps a missing link

between the earliest methods of ship building

and a method that we use today to build ships.

And this is just one of thousands, millions

of artifacts, things if we just dig underneath Istanbul

we'll find them. - That's right.

- Amazing. - That's right.

Amazing.

ERIC GELLER (VOICEOVER): 27 centuries, three empires,

one historic peninsula.

The ground is saturated, and the tiniest opening, even a hole

in a basement, might be an entrance

into one of the many unexplored layers of the underworld

of Istanbul.

It's a constant guessing game for archeologists, engineers,

and architects, and in this city the game has no end.

Fast forward 2,000 years into the future when the city begins

expanding its metro or breaking ground for a new hotel.

They begin digging a few feet beneath their modern layer,

and run into the 21st century.

What will they find that we left behind?

[music escalates]

[dramatic music]