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.