Ancient Impossible (2014–…): Season 1, Episode 10 - Extreme Engineering - full transcript

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How did the ancients
build a beacon taller

than the tallest lighthouse
in America today?

Were the ancient Egyptians

capable of creating a giant

circular saw that could cut
through solid granite?

How did Julius Caesar build a

bridge across the mighty rhine

river in just ten days and then

march his army of over
40,000 across it?

And the secrets of the greatest

harbor of the ancient
world, Rome's Portus.



Monuments more colossal than

our own, ancient super weapons

as mighty as today's, technology

so precise, it
defies reinvention.

The ancient world
was not primitive.

Their marvels are so advanced,

we still use them now.

Travel to a world
closer than we imagine,

an ancient age where
nothing was impossible.

In the modern world, iconic
manmade structures reach out

across the oceans, welcoming
beacons of progress.

The statue of Liberty, 300 feet
tall, dominates New York harbor.

But is it possible that this
engineering marvel would have

been dwarfed by a construction



created by ancient engineers
over 2,000 years ago?

And what of this, the Cape

Hatteras lighthouse
in North Carolina?

It's the tallest in
the United States.

Could there have been an ancient
lighthouse twice as high?

The answer to both these

questions lies in one
incredible structure.

It's a building that's shrouded
in legend and rumor, but not

only did it exist, it stood
for over 1,500 years.

It was the Pharos, the great
lighthouse of Alexandria.

The lighthouse at Alexandria was
the daddy of all lighthouses.

It was one of the tallest
manmade structures on Earth for

centuries and even compared to

modern lighthouses, it stood
head and shoulders above them.

This lighthouse is 85 feet tall.

That's pretty big.

The lighthouse at Alexandria
around 400 feet high.

That's impossibly big.

The Pharos lighthouse was one
of the seven wonders of the

world and deserved to be.

It was one of the tallest and
most massive buildings, and it

was built to a very, very
high standard indeed.

There'd never been anything like
the Pharos lighthouse before.

The structure of the lighthouse
at Alexandria was incredible.

It had a huge square base.

It was made of granite blocks
that were sealed together with

molten lead to protect
it from the waves.

Next came an octagonal tier and

on top of that, a
cylindrical tier.

It would've dwarfed this.

It was the equivalent
of a 40 story building.

Julius Caesar called it a work
of wonderful construction.

Modern lighthouses like this one
in happisburgh, England, are by

comparison small,
temporary structures.

This lighthouse has stood for
around two centuries.

That's better than some.

But the Pharos lighthouse, it

was built around 280 BC and

was still standing in the
1,300s, over 1,500 years.

That's unbelievable.

It was the first, the
biggest, and the best.

It set the benchmark, and when
the Romans came across it,

they saw how useful lighthouses could

be and built them
throughout their empire.

The remains of one can still be
seen in Dover, England.

Dover was the key
harbor into Britain.

The lighthouse here was
incredibly important.

This one looks impressive

the one in Alexandria absolutely
blows it out of the water.

It's almost impossible to
believe that they could martial

that kind of architectural and
engineering expertise.

But they did.

Did the lighthouse at

Alexandria really
need to be so tall?

Well, it was built for the kings
of Egypt, and they wanted to

make a grand statement.

This was built by the dynasty
of kings who succeeded Alexander

the great in Egypt.

They regarded Alexandria as a
great theater for projecting

their power and
magnificence and grandeur.

Everything had to be bigger and
better than it was anywhere else.

Bit like New York, really.

It was so impressive that
people from around the known

world travelled to see this
miracle wonder of a building.

They used to stamp
pictures of it on coins.

They used to sell models of it,

and when visitors arrived, they
could buy their ticket.

It was basically the empire
state building of its day.

It was that famous.

There's talk of an
observation platform, and I

wouldn't be at all surprised if
there were people up there

selling the ancient equivalent
of hamburgers and little models

of the lighthouse that they could
take back to to their homes.

At Dover, the Romans were
less interested in tourism.

They had an empire to build and

wanted to make sure their
ships had safe passage.

This lighthouse
didn't stand alone.

It was actually part of a pair
with another tower over there

on the Western heights, and they

stood either side of the
natural harbor in Dover.

And with a similar setup
across the channel in France,

Roman sailors could
safely navigate between the two.

By using the towers together,

seamen could effectively use an
ancient form of GPS...

To know exactly where they were
and how to travel safely and

find safe passage
to the harbors.

It was pretty clever.

At night, the Roman
lighthouses burnt dry wood to

create the brightest fire.

In the daytime, they probably

burnt wet wood, which would
create a smoke signal.

The most incredible thing about

the Pharos lighthouse is
the accounts of something

unbelievably high tech in use at

the top with remarkable similarities
to a modern lighthouse.

This is the important
part of a lighthouse.

Originally, there would have
been candle lanterns in here,

but like all modern lighthouses
we've got electricity

and we've got prisms
to focus the light.

This light from the lighthouse
can be seen 18 miles out to sea.

The Pharos lighthouse could be
seen 30 miles out to sea.

It makes you wonder what was
generating that light.

During the day a distinct
possibility would be the use of

large mirrors, which might well
have been rotated to give a

flashing effect like the sort of
thing you get in modern lighthouses.

A flashing lighthouse
just like today's

over 2,000 years ago.

This sounds impossible, but
model maker Richard Windley has

recreated how it
might have worked.

My theory, and it is only a
theory, is that a mirror would

collect the sun's rays from
somewhere in this direction into

this top mirror which had to be
precisely angled so that the

beam went absolutely
vertically down below.

The beam would be reflected down

below to the mirror here, which

then could be rotated to

distribute the light, a bit in

the same way as a modern
lighthouse would do.

A great mystery has

arisen behind the use of
mirrors in the Pharos.

Could there have been more to

them than just providing
safe passage?

We are told that the mirrors

could be used to concentrate the

rays of the sun
to destroy ships.

An incredible ancient
weapon, like something

from the space age.

Could it have been true?

Alexandria was home to the
greatest library of the ancient

world, and the city
wanted it protected.

But even if there was no

super weapon, just the rumor of

one would have been enough to

make anyone think twice before
attacking Alexandria.

It wouldn't do any harm,
would it, if the word got out

that they had a kind of super
ray gun on top of the Pharos

lighthouse that could destroy

ships, very much, "don't
tread on me or else."

The lighthouse was certainly
in a good defensive position.

That's why today, this

15th century fortress
marks the location.

With or without the ancient

super weapon, the Pharos of

Alexandria was one of the most

extreme examples of
ancient engineering.

The lighthouse at Alexandria

was truly a wonder of the

ancient world, the size
of a modern skyscraper.

Even today, it would be thought
of as an amazing feat.

It's never been bettered.

The Pharos was built so
well that it took multiple

Earthquakes to eventually bring

it down in the 14th century.

It was a dramatic end to an

incredible construction.

Many of the most incredible
engineering projects

of the ancient world happened in

Egypt thousands of years ago.

They built amazing structures,
incredible temples and tombs,

the great sphinx, and
the pyramids at giza.

But now there's evidence of more
impossible engineering.

This mysterious stone slab was

found at Abu Roash, site of the

unfinished pyramid
five miles from giza.

It was discovered near an
ancient boat pit in which a

boat would have been buried to

transport a dead king
to the afterlife.

Remarkably, the slab seems to

suggest that the ancient

Egyptians were using engineering

techniques thought unknown until
the 19th century, four and a

half thousand years
later, surely impossible.

The slab is made of granite,

which is one of the
hardest rocks.

We know that the Egyptians used

copper tools, but copper
is softer than granite.

And they managed to cut
the granite so finely.

How did they do it?

I find this line
really intriguing.

I mean, if traditional theories

are correct for how they would
have polished this surface,

there's no real reason that
there should be this line.

That line really to me
looks like a cut mark.

Let me show you something else
which is really interesting.

If you put a horizontal right

across the block, what you can

see is that it's a
very concave surface.

It's quite nice and uniform, but

you can see it bows
significantly in the middle.

The smoothness of the cut
can only have been made

by sawing rather than hacking.

The curvature of the rock
suggests a particular type of

saw, an impossibly modern saw.

The most controversial theory
for how this granite slab could

have been formed this way, to
have a concave surface, is by

cutting it with a
giant circular saw.

It seems amazing of course

because no circular saws have

ever been found
in ancient Egypt.

This would be astonishing.

According to the history books,
the circular saw was invented at

the end of the 18th century.

If these curves can be

reproduced, perhaps it would be

possible to deduce
how they were made.

At this stone cutting factory

near yeovil, England, they've

been trying to find the answer.

They have to have been using

a technology that is more

advanced than we've given credit

for, and I'd love to
find out what that is.

Producing the curved
profile is achieved with

a modern circular saw by moving
the saw across the stone.

Could an ancient circular
saw have cut like this?

But with the saw vertical to the

rock, a straight lip
is made at the end.

The Abu Roash slab has a curved

lip, as if the saw
came in horizontally.

You can see here that if we
do a cut straight on to the

surface, you will actually get a

surface curve like that, that
you see at Abu Roash.

But the Abu Roash slab has this
most unusual thing inasmuch as a

compound curve, and that can
only be done by bringing the

blade in at 45 degrees to the
surface and drawing the slab along.

That reproduces exactly the
pattern that we see on the slab.

At an angle of 45 degrees,
a circular saw gives a

curved profile to match
the curvature of the saw.

It also leaves a curved lip
whether it's the blade moving

over the block or, more likely,

the block being moved
against the blade.

If you have the saw in a
vertical plane, you are

effectively moving
the block like that.

That's a perfectly easy motion

to do if you have some rollers

and some people to move it.

But the ancient
Egyptians didn't have

electrically powered
machinery like this.

And granite has to be cut with

either high tensile steel
or diamond blades.

The Egyptians didn't have steel,

and cutting rock with
diamond tipped saws is

impossibly advanced engineering.

In fact, there's no evidence

that the Egyptians had
even discovered diamonds.

If the ancient Egyptians had
engineering like this, history

would have to be rewritten.

The intriguing thing now is
if you look at those two

curvatures, one in the flat
plane and one in the vertical

plane, and you extrapolate those
circles back, you come back to a

saw that's about 30
foot in diameter.

And that's very big.

A 30 foot circular saw.

It would have to have been vertical for
slabs of stone to be easily fed in.

In fact, it would have to have

been in some kind of
specially made hole.

So you're looking for a pit

in the ground about
10 or 12 feet deep.

Lo and behold, next door to the

slab, there is a slot in the

ground which exactly matches the

dimensions of a saw that would

have to be used for
that slab here.

So I'm saying here, here's a

slot alongside a pyramid
that is not a boat pit.

These slots have been
mislabeled as boat pits.

Could some of these pits really
have contained giant circular saws?

This would be incredible.

And what about the diamond?

No trace of diamond has been
found in any excavations.

They weren't looking for
particles of diamond.

So I'm saying that next time a
boat pit is excavated, a new one

they've found, I suggest they
look very carefully at the ends

and do a very careful analysis
of the sand they find there.

If they find the sand contains
diamond, there's your smoking gun.

That's the thing that will prove
they were saw pits, not boat pits.

But one piece of evidence has
been found, and it's rock solid.

The strongest explanation for
the Abu Roash slab could be a

giant circular saw strong
enough to cut through

granite four and a half
thousand years ago.

The extreme engineering
of the ancient world

made mega builds that
still amaze us today.

2,000 years ago, Julius Caesar,
one of Rome's greatest

commanders, faced an
impossible challenge...

A quarter of a mile wide and
30 feet deep the river rhine.

From the far bank, raiding German tribesmen
threatened Caesar's new conquests.

On this side, the germanic
tribes were quite happy.

They believed that any advance
across the river was impossible.

But the Germans underestimated
the engineering

power of the Roman army and the

all consuming
ambition of Caesar.

To understand how the Roman army

could bridge a river 2,000 years

ago, we're looking at how the
British army does it now.

Modern armies have access to
high tech bridging equipment.

So to cross this river today,

we've called in some help from
the royal engineers.

These three high mobility
trucks can deliver

an instant bridge
anywhere and at any time.

This is "able," automated
bridge laying equipment.

Ten men can lay this 100 foot

bridge in less
than half an hour.

But Caesar's bridge would need

impossible vital statistics

as long as four football fields

and supporting the
weight of 40,000 troops.

How did the Roman army achieve

this impossible task thousands

of years before modern
mobile bridging equipment?

There's a fascinating clue here

in ehrenbreitstein fortress,

high above the river rhine.

These very substantial pieces

of oak were recovered from the

bed of the river rhine
not far from here.

They've been carbon dated
back to 50 years BC

There's only one explanation for

that these were part of
Julius Caesar's bridge.

These piles driven into
the riverbed reveal the

type of bridge Caesar built.

They've been shaped by Roman

engineers so they could be

driven into the riverbed.

But when they were driving into
the bed they weren't quite sure

what they were going
to come across.

They put pile shoes on the bottom so it could
be driven in without splitting the wood.

And it seems almost

unbelievable, but this nail was

driven in by a Roman engineer.

But these piles were one
and a half feet thick,

60 feet long and
weighed over 2 tons.

How did they get them in?

Today we use pile
rigs like this.

It uses a 5 ton hammer and can drive
60 piles a day it's quite amazing that

Caesar 2,000 years ago was doing

exactly the same type of thing

in order to get over
the river rhine.

Just think about the size of

this engineering challenge.

You've got to drive supports

into the bottom of the river.

You've got to put beams across.

And then you've got to
build a road on top of it.

But the supports were massive.

You couldn't just knock them in
using a big hammer.

It seems impossible to
believe, but Roman soldiers

built their own pile drivers.

A system like this,
it uses gravity.

At the top, we've got a
great big granite block

that gets pulled up on
a block and tackle.

Let it go ba dunk!

Thumps and drives
it into the ground.

They had their tools.

They had trees.

They made this.

It's beautiful.

And these amazing pile
drivers could float.

When we look at modern military

engineers constructing a bridge,

the principles haven't
changed in 2,000 years

the lessons come all the way
back from Caesar's time.

As this rolled out in sections

and another section was dropped

in, that's exactly what
Caesar's army did.

This amazing bridge

created from the forest advanced

across the river rhine
impossibly fast.

It took just ten days.

Ten days that must have been
absolutely astonishing to the

Germans across the river.

A bridge that, in effect,
secures the borders of Rome.

To defeat the strong
currents of the rhine,

Roman engineers created design features we
can still see today in modern beam bridges.

You may think initially that

what you should do is
put them in vertically.

No.

The Romans had a cracking idea.

You put them in at an angle.

That's upstream, so the force of
the water is pushing them even

more into the bed of the river,
making it stronger.

For the terrified Germans,
Caesar's bridge was an

unimaginable display of
extreme engineering.

But that didn't stop
them from attacking it.

The germanic tribes realized

they could float logs down the

river to try and take out the
bridge that was being built.

And to get over that, what the

Romans did was put piles in
upstream just to deflect and

slow down any logs that were

sent down to try and
wipe out the bridge.

With the bridge complete,
Caesar led his troops

to face a German army that
outnumbered him 10 to 1.

But the awestruck Germans fled.

Caesar's bridge enabled him to subdue the
German tribes without having to fight them.

This intimidating feat of

extreme engineering wasn't
just a mighty bridge.

It was the ultimate
strategic deterrent.

It was a phenomenal bridge.

Put that into context: During
the second world war, a bridge

was put across the
Sangro river in Italy.

Slightly less, just over 1,100
feet, and it took them 9 days.

So in Roman times 1,300 feet, 10
days, second world war, 9 days.

This really was a massive

statement by Caesar and his
armies.

This was "we are Rome. We can go
where we wish. Bow down before us."

Today's deepwater ports are amazing
feats of engineering built to

accommodate huge container ships

and millions of tons
of cargo every year.

We're here in the
port of San Diego.

Ports like this are really the
lifeline of a nation.

Cargo from all over
the world comes here.

This is one of the most important ports
on the west coast of the United States.

But ports were even more
important in the ancient world.

Whole empires depended on them,

and none more so than Rome.

And the port of Rome, being the

greatest of its kind, is
simply known as Portus.

Portus was the major seaport

that served the imperial
city of ancient Rome.

It was about 20 miles outside
the city, but it was linked to

canals that took grain and other

cargo directly into the
heart of the city.

But there was one significant
difference between

Portus and many of our
great modern harbors.

Portus was manmade.

San Diego is a natural

harbor, one of the best
harbors in the world.

Unlike San Diego, most of the areas around
the mediterranean had no natural harbors.

Portus had to be built by hand
to make it every bit as

important as this
harbor right here.

To build a harbor by hand is
a mammoth engineering feat.

And for the Romans to achieve
this 2,000 years ago on the

scale of Portus is a seemingly
impossible achievement.

The harbor infrastructure at Portus
was incredibly sophisticated.

The main basin was almost 22

million square feet
in surface area.

It had wharves and jetties,
a shipbuilding area.

This was fantastic engineering.

The scale is simply
astonishing, and to try to get a

sense of it, at the University
of Southampton in England,

they're using the latest computer imaging
techniques to re create the ancient port.

It's very much as if we're walking about
the site of Portus, even though at the

moment we're based here in
the lab in southampton.

Data from geophysical
surveys, laser

imaging and photos taken from

drones are all fed
into computers.

This is cutting edge
archaeology, and what they've

unEarthed is awe inspiring.

We're talking about something

at an incredible scale.

For the visiting provincial in

their sea going ship, this was

the first sight of Rome.

This was meant to really knock

you for six and say, "oh, my

god, I'm really arriving in the

center of the world here."

There was the massive
imperial palace, at

least three stories high.

And this ship repair building,

impossibly big,
nearly 800 feet long.

This is an absolutely enormous
building, truly awe inspiring.

The logistics, the manpower,

the scale of everything involved

is quite... overwhelming.

Portus wasn't the only artificial
harbor in the ancient world.

Incredibly, in the 3rd century

BC, a huge harbor was made at

carthage on the north African

coast, at that time,
Rome's great rival.

It was big enough for over 200

ships to be built and serviced there.

The outer part was for merchant

ships and then there was a hidden
inner harbor for warships.

But typically, the Romans took
things to another level.

Portus was over
ten times bigger.

Why did the Romans go to
such superhuman efforts?

Why was such a huge port needed?

In the 1st century, it's
estimated that the population of

Rome was about a million people,
and that was too many mouths to

feed from just the surrounding
agricultural land.

So they needed to import grain

into the city, and that's
where Portus was key.

To prevent food riots,
vast amounts of grain

were imported from
Egypt and from sicily.

If you keep the people
fed, you keep them happy.

If they're starting to get
hungry, if there isn't food

available, if the shops are
empty, there's trouble.

As the empire waned in the
6th century, so did the

use of the port, and
it began to silt up.

Eventually, buildings
fell into disrepair.

But seeing the port come alive

again gives us a sense of the

reach and might of Roman
power at its height.

The amazing thing about

Portus is the scale of remains
that we have to encounter there.

And, in turn, they give us a way
into understanding the sheer

scale of the Roman empire
that it was at the heart of.

The greatest empire
needed the greatest port.

And they wanted everyone else to

see that they had it.

That's why they put so much

effort and invested so much time

and engineering skill into
Portus.

They created one of the
masterpieces of the ancient world.

Rome excelled in
extreme engineering.

But hundreds of years
before Roman records...

This tunnel was built
without power tools...

Without tunneling machines...
Without dynamite.

And these ancient engineers
surveyed so accurately that to

this day, we don't
know how they did it.

This is lake nemi, 19 miles
south of Rome, Italy.

Every year, rainwater flooded

the lake, making rich
agricultural land unusable.

To solve the problem, ancient

engineers achieved the

impossible by tunneling
right through a mountain.

There's a fantastic
construction right over here.

Essentially, it is a tunnel used

to drain away part of the
water from the lake.

But you've got a
mountain in between.

It's estimated that this tunnel
was started over 2,500 years ago.

And to speed up construction,

the builders dreamt up
an impossible plan.

"Why not build a drainage tunnel
right through the mountain?

But not only that, let's start

at both ends and see if we can
meet in the middle."

Now, that's a major challenge.

Modern engineers struggle with

that, but the ancients did it.

3D analyst James Dean
is using the latest

technology to understand this
feat of extreme engineering.

This incredible tunnel, built
to drain and regulate the

overflow, runs downhill from
lake Nemi into this valley.

Two tunnels were dug, one from

each side, with the aim
of meeting in the middle.

The tunnels met just nine
feet out vertically.

This tunnel was dug over two and

a half thousand years ago.

As a feat of human endeavor,
it's just incredible.

But it seems totally impossible

they could survey
it so accurately.

How did they do it?

Modern tunnelers use lasers
to dig a straight line.

It seems impossible that ancient

engineers achieved this
thousands of years ago

it is wet.

It is damp.

It is freezing.

And then of course, I've got

electric lights, but what do

they have in antiquity?

You had oil lamps,

little niches that you would just
carve into the side of the rock.

It's pretty pitiful.

And yet the engineers were
astonishingly accurate.

Over a mile, this tunnel
drops 41 feet, an average

gradient of under one percent.

It's an extraordinary feat
of ancient engineering.

Just two reference shafts were

dug to make sure they dug
in the right direction.

But how did they get
the gradient right?

They might have used this

rudimentary Roman spirit level,

a water trough with a mark at

each end to show the
correct incline.

The ancient tunnelers may have
used this to harness gravity.

We don't even know if this
instrument existed so early.

But we do know they somehow
achieved the impossible.

Whatever methods the
ancients used, the evidence

that they achieved the

impossible is here,
450 feet underground.

Ah, all right.

Now, you have Paulo up
there, and I'm down here.

And what it represents
is the two teams.

So up on top from lake nemi, we

have the workmen cutting through

and progressing about
3/4 of a mile.

But down below where I am, the

other team was moving more

slowly because this
stone is so hard.

It's basalt stone.

So they only move 1/4 of a mile.

We still don't really
know how they did it.

And the two tunnels met inside

the mountain, and they
were just a few feet out.

That's without any
modern technology.

It's incredible.

And it was 400 to 500 years BC

It appears impossible,
but they did it.

Regulating the level of
the lake didn't just

protect farmland.

Several hundred years later, the

Nemi tunnel enabled the emperor

Caligula to build a vast

floating palace and a temple
to the goddess Diana.

And 2,000 years later, the

tunnel enabled the lake to be

drained to reveal
caligula's ships.

It's incredible to think that

you have this tunnel 2,500 years

old or older draining out part

of lake nemi with the same

tunnel to reveal the
great ships of caligula.

Without the nemi tunnel
to take away millions of

gallons of water, the two

greatest ships to survive from

the ancient world would
never have been recovered.

And even today, the tunnel could

protect the lake from flooding.

Today, every great city
has a world beneath it

tunnels, vaults,
sewers, pipelines.

This is extreme
modern engineering.

But could there have been

underground engineering 1,500

years ago on the scale of a

subterranean cathedral?

Surely impossible.

In modern times, one of the most

remarkable underground
constructions was built in

London, England, in
the 19th century.

I'm here in finsbury
park in north London.

I'm about to have a look at one of the
subterranean wonders of this city.

Dr. Bradley Garrett is
an expert in the hidden

worlds beneath our cities.

These steps lead to an
engineering marvel.

It's an empty victorian cistern,

an underground reservoir that

provided water for
the city above.

Others are still in use beneath

London and together they're

quite rightly famed as a wonder

of the victorian age.

This particular reservoir
would have held something like

five million gallons of water.

This is an incredible piece of

architecture and not only
a feat of engineering,

but an aesthetically
very beautiful space.

Incredible engineering like this

kick started the modern world.

But on the other side of Europe,

there's a modern city
with an ancient past.

This is Istanbul, and beneath

these streets is
something extraordinary.

Perhaps our modern engineering
isn't so modern after all.

I'm in the basilica cistern,

which in turkish is known as

"yerebatan sarayi," or
"underground palace."

And this is the largest water

cistern in the city formally

known as constantinople.

The basilica cistern
is incredible.

It's massive, and it can hold
up to 100,000 tons of water.

That's 22 million
gallons of water.

The walls are 12 feet thick

lined with waterproof cement.

It still works.

It still holds water.

Today, this would be
an astonishing feat of

engineering.

But incredibly, this
cistern is Roman.

The groundbreaking, 6th century

construction was overseen by the

Roman emperor himself,
justinian, successor to

constantine and a man
eager to make his mark

it's said that the basilica
cistern was built by 7,000 slaves,

all under the command of
emperor justinian himself.

This was engineering
on a monumental scale.

To think that they undertook

such a grand building project

with what are basic and simple

tools and methods is
kind of beyond belief.

To a modern engineer, you'd

think you just wouldn't
be able to do it.

How did they build it?

What was the engineering
that was involved?

Well, essentially, you had a

massive labor force that
dug out this space.

We're talking about men using

pick axes and shovels and wicker

baskets to haul away the dirt.

What's even more impressive of

course is that that simple kind

of technology, what they had

available to them, still allowed

them to build greatness.

This is like a cathedral.

The cistern could be a
temple to Roman engineering.

In fact, many of these 336

marble columns came from disused

temples across the empire.

The Romans are recycling a

lot of marble for the cistern.

They also recycled this, a

great discovery, and
it is a medusa.

This is one that wards
off evil in pagan times.

She's placed here and stacked
with other blocks to get this

smaller column up to the full
height of the ceiling.

Is there some hidden meaning in

the fact that this
head is upside down?

Well the thing is, this was in

the cistern in the 6th century.

It was underwater.

Beyond that, we don't know.

But why have a water
supply underground?

Other cities were supplied with

water from reservoirs,
aqueducts, and canals.

The Romans were experts at this.

A few hundred years before, the

Romans in the east had found out

the hard way the value of

cisterns in times of war.

For months, Jewish rebels on the
hilltop fortress of Masada had

held out against a massive Roman
force, and they were able to do

so because the underground
cistern provided them with

enough fresh water
to endure the siege.

In Constantinople, the Romans
were determined that they would

have a secure supply of water in
the heart of the city.

The city is impervious to
attack, so if they're being besieged,

they're going to have
a massive water supply.

They've got that large supply.

They can withstand attack
for a very long time.

It's a great engineering
solution, and you wouldn't see

a water supply on this scale
for another 1,400 years.

Constantinople may have
had the biggest, but it

wasn't the only city in the

ancient world with
underground cisterns.

The people of Alexandria did
exactly the same thing.

They built cisterns
under their city.

It just goes to show how clever

all these ancient civilizations

were and how good they were at

engineering solutions
to the problems.

The basilica cistern
remained unparalleled

until well into modern times.

This is extreme
engineering at its best.

It's astonishing to think

that their work wasn't
bettered for 1,500 years.

Ancient engineers set the
standard for technology

that forms a vital part of our

modern world, from sophisticated

navigation systems to
precision cutting...

And ultra modern seaports,
proving that the ancient world

was able to achieve the
impossible, creating extreme

engineering that can still
take your breath away.