All language subtitles for Ancient Top 10 S01 E05_track3_[eng]

male narrator: An industrial
super factory

thousands of years
ahead of its time...

‐ This really was the world's
first mega factory.

narrator: A huge
2,000‐year‐old building

that grows stronger
the older it gets...

‐ It's an enormous space.

You could hold over
5,000 people.

It's absolutely amazing.

narrator:
A revolutionary machine

that transformed cities...

‐ If you can lift more,
you can build bigger.

narrator:
And the most ambitious

Roman engineering project
of them all.

‐ Huge networks
transporting gallons

upon gallons of water
across the empire.

narrator:
Where will they be ranked

in the only top ten list

thousands of years
in the making?

[dramatic music]

♪ ♪

Rome engineered an empire

which stretched from
the Atlantic to the Tigress.

At its peak,
there might have been

up to 70 million citizens.

The Romans shaped our world

more than any other
civilization

from antiquity.

This week's "Ancient Top Ten,"

Rome's Greatest Hits,

amazing Roman feats
of engineering ranked

by experts according to which
most changed the world.

♪ ♪

At number ten,

courtesy of Julius Caesar,

the bridge that beat
the barbarians.

‐ Caesar's bridge
over the Rhine

is incredible engineering

amazingly executed.

♪ ♪

narrator: In 55 B. C.,
Rome's greatest general,

Julius Caesar,

decided to launch an attack
on the hostile Germanic tribes.

He wanted to expand
and secure his empire

into what is now
modern‐day Germany,

but how was he going
to get his whole army

of 40,000 men across the river?

Most leaders would
simply go around it,

but Caesar wasn't going to let
anything stand in his way.

‐ Caesar couldn't wait,

and he wasn't willing to accept
that something couldn't be done.

And in typical Caesar fashion,

he was willing to try something
bold and audacious.

narrator: Caesar's plan
was an engineering breakthrough

and clearly demonstrated

the strength
of Rome's power

to their enemies.

‐ This river had never
previously been bridged.

This was a hugely
ambitious project

at the very edge
of the Roman world.

♪ ♪

narrator:
Bridge building at that time

normally took months,
if not years.

Julius Caesar did it
in a matter of days.

‐ Caesar was trying to cross
the Rhine at a point

where it was
1/4 of a mile wide.

So that's crossing a span

that's as long as the
Empire State Building is tall.

narrator:
The Rhine wasn't just wide.

It was 30 feet deep

with strong currents.

♪ ♪

These are military engineers
in today's British Army.

They have modern, high‐powered,

mobile bridge‐building
equipment.

♪ ♪

But Julius Caesar had
to start from scratch.

‐ 40,000 Roman troops
start chopping down

all the trees in the area.

They didn't just need timber
for the bridge itself.

They also needed timber
to create a huge floating crane

and an enormous pile driver.

narrator: The pile driver would
hammer in giant wooden stakes,

which would give
the bridge stability

and allow it hold the weight
of Caesar's massive army.

This wasn't a standard
method of construction.

It was revolutionary
engineering,

and the Romans were
inventing it on the spot.

With the piles in,
the bridge advanced the length

of three school busses
every day.

That's faster than modern
engineers can do.

‐ The Germanic tribes were
on the other side of the river

thinking they were safe,

and you can just
imagine their horror

when this bridge started
to creep towards to them.

narrator: The bridge
took just ten days.

It was long enough
and strong enough

to hold the entire army.

‐ It was a real incarnation

of the might that was Rome.

♪ ♪

‐ The barbarians
actually outnumbered

the Roman soldiers ten to one,

but they were so intimidated
by the speed and the efficiency

with which this bridge had been
built over their river,

that by the time Caesar
and his troops crossed over,

they'd all fled the area.

[all yelling]

Caesar had won the battle

without the loss
of a single Roman life.

‐ Caesar was the master
of the publicity stunt.

He marched across this bridge

and said,
"Here I am.

I can do whatever I want."

Then he marched back
and tore it down.

narrator:
The bridge was destroyed,

but the point had been made.

‐ It cemented Rome's reputation
as a military might

more than any bloody battle
would have done.

♪ ♪

narrator: And the bridge
was an early example

of using piles for support.

♪ ♪

Today, steel and concrete piles

are the norm
for making things stable.

Caesar and his engineers

were thousands of years
ahead of their time.

♪ ♪

Like Caesar's bridge,

the next Roman marvel
on our countdown

was also the product
of the mighty Roman military.

♪ ♪

Shooting in at number nine,

the repeating ballista,

also known as the polybolos.

‐ It's a Gatling gun.

The same idea as today,
but 2,000 years ago.

narrator: The Roman army
couldn't be matched.

Organization, tactics,
weaponry.

Their weapon of choice
was the ballista,

a giant wooden crossbow

that could launch bolts
a quarter of a mile.

But they were always
looking to improve

and to make their weapons
even more deadly.

♪ ♪

The Romans inherited
a new design from the Greeks,

and took it to another level.
A repeater.

This was the machine
gun of its day.

‐ The repeating ballista
could fire one bolt

about every ten seconds,

which doesn't sound like
that much until you realize

that it actually tripled
the rate of fire

that the Romans
had previously had.

♪ ♪

This was a devastating weapon.

‐ It was a barrage.
It was a deadly rain of bolts,

and we're talking 1,500 years

before the first
artillery barrage.

♪ ♪

narrator: A repeating weapon
was sophisticated

ancient engineering.

It had a gravity‐fed magazine,

which would be constantly
dropping bolts down one by one.

Winding the mechanism
pulls back the string,

and the ballista fires
automatically.

As long as the magazine
was kept loaded,

this ancient machine gun
could fire continuously.

It's known as a chain drive,

and it was the first
in Western technology.

‐ The Roman engineers
were the first people

to master the chain drive.

They were so ingenious.

narrator:
Years ahead of its time,

this technology
wouldn't be seen again

until the 16th century
when Leonardo da Vinci

supposedly reinvented it.

The engineering genius
behind the polybolos

was centuries
ahead of its time.

‐ Amazingly, there's nothing
as effective on the battlefield

for over 1,000 years.

narrator: It was the pinnacle
of Roman military engineering,

and the principles behind
the polybolos underpin

our modern mechanics today.

♪ ♪

The development of technology

has seen our cities advance
at a staggering pace,

but our survival still
depends on the one basic need

that hasn't changed
in millennia,

water.

Coming in at number eight,

it's the Basilica Cistern
of Constantinople,

modern day Istanbul.

A giant underground reservoir

providing a clean,
safe water supply.

‐ Underneath modern‐day Istanbul
there's a subterranean treasure.

It's the Basilica Cistern.

It was actually dug out
by 7,000 slaves

working in appalling conditions

so it's a wonder
of the medieval world,

but it has a very dark history.

♪ ♪

narrator: The Basilica Cistern

was built was not only to be
a source of water,

but to form part
of the city's defenses.

♪ ♪

The cities of the Empire

were a prime target
for invasion.

They would be taken by force,

and the best way to do that
was with siege warfare.

‐ As long as we've had
cities and fortresses,

we've had siege warfare.

The defenders
have to wait it out.

The attackers have to find a way
to starve them,

thirst them,
or just make them give up.

These things can take years,
and if you think about it,

it really is just
a tactical chess game,

and who's gonna win?

It might take forever
to find out.

♪ ♪

narrator:
In ancient times,

for a city to be secure

and to withstand a siege,

it took more than strong walls
and an army.

What was needed most was
a safe supply of water.

‐ If there's no water
inside the city,

then you can be held to ransom.

narrator:
And having it underground

meant it was protected.

‐ As soon as you can secure
a water source inside the city,

in a cistern, for example,

you have got the upper hand.

narrator: And that's exactly
what the Romans did

at Constantinople.

But this city's incredible
piece of engineering

lay hidden beneath the streets,

a secret for hundreds of years.

Number eight in our countdown.

♪ ♪

‐ 500 years ago in Istanbul

there were people
in residential neighborhoods

who were able to open up
the floorboards

and the stones of their houses,

lower cups and jugs down,

and bring up water for drinking

and washing their clothes.

♪ ♪

They launch an expedition,
they dug down deep,

and they found
the Basilica Cisterns.

♪ ♪

narrator:
The Basilica Cistern,

deep underground,

but today open
for the public to view.

Over 400 feet long
and 200 feet wide,

the biggest and most
magnificent cistern

in antiquity.

It's as big as
an underground cathedral.

336 marble columns were brought
in from disused pagan temples

from across the Empire.

‐ Of all the hundreds
of columns,

there's one that
I love the most.

It's a shorter one,
and it's propped up

by a reused block.

And what's on that block

is a beautifully
carved Medusa face.

It's absolutely exquisite.

narrator:
It's believed the Romans

transferred this sculpture

from another temple

in order to keep
construction costs down.

‐ The Romans were nothing
if not practical.

narrator: The Basilica
Cistern wasn't the only

sophisticated water system
in ancient times.

♪ ♪

In 73 AD,
there was an uprising of Jews

against the Romans.

Despite being surrounded
and their supplies cut off,

a rebel force was able
to hold out for months

in the mountain fortress
of Masada,

in what is modern‐day Israel,

thanks to a cistern providing

a ready supply of fresh water.

And Alexandria in ancient Egypt

had a remarkable cistern
under the city,

making it a major stronghold.

But the water supply
delivered to Constantinople

by the Basilica Cistern
was unmatched.

It was the largest
and most impressive

in the ancient world.

♪ ♪

‐ The Basilica Cistern
was huge.

It stored 22 million
gallons of water,

so that gave Constantinople
its strength and its security.

It meant the city
could not just survive,

but thrive.

narrator:
This engineering marvel

would not be bettered
for 1,500 years.

The Romans used advanced
technology and engineering

to ensure that the cistern
was built to last.

‐ The walls of the Basilica
Cistern are 12 feet thick

and they're lined
with waterproof cement,

and it still works.

It's not a ruin.
It still functions.

It still holds water.

narrator:
Thanks in part to

this incredible piece
of Roman engineering,

Constantinople was able to

withstand repeated sieges

for nearly 1,000 years
to overtake Rome

and become the greatest city
in the world at the time.

♪ ♪

Control of water
was also behind

the next engineering great.

At number seven...

♪ ♪

The Nemi Tunnel.

♪ ♪

19 miles south of Rome
is a sacred lake,

Lake Nemi.

♪ ♪

In the early Roman period,

the lake was prone to flooding.

At the lakeside was a temple
to the goddess Diana,

and allowing her temple to
flood was simply unacceptable.

The Romans came up
with an extraordinary solution,

to build a tunnel
through a mountain.

‐ And this is exactly
the sort of thing

that the Romans would do,

a giant overflow pipe
on a monumental scale.

♪ ♪

‐ The Nemi Tunnel was over

a mile long
through a solid mountain.

This is ancient engineering
at its most sublime.

♪ ♪

narrator: The tunnel was
built around 500 BC.

♪ ♪

Constructing any kind
of tunnel back then

was an extraordinary feat,

let alone one this long.

♪ ♪

And 2,500 years later,
it's still intact.

‐ The Nemi Tunnels
were actually dug out by hand.

This was harsh,
horrendous manual labor,

but they persevered to the end

and dug out a staggering
5,000 feet.

narrator: The Roman workers
only had simple tools

and just the light
of small oil lamps.

In the tunnel it was dark,
cold, and wet,

but this tunnel was built
with such accuracy,

even modern engineers
would struggle to match it.

Today, we use lasers to tunnel
in a straight line.

Unbelievably, the Romans
started digging from both sides

of the mountain at once,

and, somehow,
met partway through.

‐ It's absolutely incredible.

How could they build this
without modern building

and surveying equipment?

narrator: Two tunneling teams
worked independently

with incredible precision.

♪ ♪

When they met,
the paths they dug

were within ten feet
of each other.

‐ Both sides meeting with pretty
impressive accuracy,

and it travels across
an impossibly gentle gradient.

♪ ♪

‐ The tunnel's over
a mile long,

and in that entire distance,

it drops by just 41 feet.

That's an average gradient
drop of less than 1%.

narrator: Even today, we don't
know exactly how they did it.

It could be an example
of skills and technology

that have been lost to time.

This workmanship
has kept the tunnel in use

right up to recent times.

♪ ♪

In the 1930s,

the Italian dictator Mussolini

used it to drain Lake Nemi.

He wanted to recover
what lay at the bottom,

the priceless remains
of two ships

built for the Roman emperor
Caligula.

The lake gave up
its secrets,

but the tunnel's
impressive construction

still remains a mystery.

♪ ♪

Our next invention uncovers
the dark side of the Romans,

and it only came to light
after the discovery

of a mysterious ancient wheel,

the likes of which have
never been seen before.

It led historians
to a Roman underground hell

that would claim
the lives of countless slaves.

Rolling in at number six...

[dramatic music]

Is the underground hell

of the silver mine
at Rio Tinto.

♪ ♪

The Roman Empire spread
all the way from Britain

to the Middle East,

but it was here,
in the hills of southern Spain,

that 100 years ago,

the remains of this strange
wooden wheel were found.

What could it be?

It was soon discovered
to be Roman,

and it was over
2,000 years old.

‐ What the experts soon
realized was that

they discovered
a giant water wheel

14 1/2 feet in diameter.

And the most amazing thing,
it hadn't been buried.

It was supposed
to be underground.

narrator: This water wheel
was part of the machinery

of an ancient silver mine

known as Rio Tinto.

Precious metals
like silver and gold

were crucial
for the Romans.

Their huge empire
needed paying for.

Massive building projects,
the military,

and their administration.

Somehow,
this all needed to be funded.

‐ The 60 million citizens
of the Roman Empire

needed a currency to trade in.

To get that currency,
they needed pure silver.

narrator:
In order to get this silver,

they constructed
underground mines,

but they had a problem.

The mines were prone
to flooding

from subsurface water supplies,

so the Romans constructed
huge water wheels.

They were used to drain
the water away from the mine.

How was this done?

Buy the feet of slaves.

‐ Huge underground water wheels
being walked on by slaves.

It's crazy, isn't it?

Would you have liked
to be the Roman engineer

who floated that idea?

They must have thought
he was nuts.

narrator: Incredibly,
there were eight pairs

of wheels raising the water
from one cavern to the next

and up out of the mine.

Once again,
the Romans were using

their engineering genius
to overcome nature.

‐ The whole system
could lift water

the height of
a ten‐story building.

narrator: These astonishing
wheels never stopped.

They were worked
24 hours a day.

‐ It's estimated that
one slave could raise

21 gallons of water per minute,

so that means the whole system
could lift 180,000 gallons

of water every day.

narrator: But the water
was full of poisonous minerals,

which made the air toxic
to breathe in.

‐ Imagine, you're underground,

the air is toxic

from the fumes
emanating off the water.

It must have been
absolutely horrific.

♪ ♪

‐ They were terrible
conditions to work in,

and once the slaves
were down there,

they would most likely never see
the light of day ever again.

narrator: Most of these slaves
didn't live much over a year,

and when they died,
the Romans didn't even bother

taking their bodies
to the surface.

‐ This worked out fantastic
for the Romans,

but not so well for the slaves.

It's impossible to imagine
the horrifying lives

that the slaves endured
down in the mines.

narrator:
Sacrificing lives

for an incredible
feat of engineering.

This was typical
of the Romans.

Without mining
the riches of Rio Tinto,

the empire would never have
been able to expand so far.

♪ ♪

A growing empire
brought with it

a growing population.

They all needed to be fed,

so the Romans used technology

to do it on a massive scale.

Next in our countdown is
an extraordinary food factory.

It could be described as
Roman fast food.

Coming in at number five...

♪ ♪

The amazing water mills
of Barbegal.

♪ ♪

This is Barbegal
in southern France,

near the city of Arles.

♪ ♪

In the 1940s,
experts realized

that these strange ruins
were the remains

of something
truly spectacular...

♪ ♪

A series of water mills
producing huge amounts

of flour thousands of years

before the industrial
revolution.

To this day, there has never
been anything else like it.

‐ It's an industrial
super factory, and it's Roman.

narrator: Water mills
were already used

in food production
individually.

The ancient Chinese had them
and the Greeks too.

But mills linked together
was something completely new.

It was a huge
technological leap.

‐ They didn't just have
one water wheel, they had 16.

This really was the world's
first mega factory.

‐ The water flowed through
a series of mills

powering each one in turn.

Now, that's only
a drop of 65 feet,

but each water mill
is going to be receiving

33 gallons of water
every second.

That's a huge energy output.

narrator: Unlike
most conventional water wheels

which were powered
by the flow of a river

at the bottom
of the wheel,

these were overshot
water wheels,

the difference being that
they were powered by the water

dropping on the wheel
from above,

a much more powerful method.

The construction
of this new system

was a huge technical challenge.

‐ To power these water wheels,

the Romans actually diverted
a nearby aqueduct.

♪ ♪

And even more impressively,

they cut a channel
through the solid rock

of a mountainside
to create a passage

for the water
to reach the wheels.

♪ ♪

‐ Enough flour was made there

to produce 9,000 loaves of bread
every single day.

narrator: That's 4 1/2 tons
of bread daily.

This was enough to feed
the Roman troops nearby

as well as the recently
conquered Gauls in Arles.

If their new citizens
were fed and watered,

the Romans knew they would
be less likely to rebel.

As well as grinding flour,

the mills could be used
for other purposes too,

such as powering
mechanical saws.

Barbegal might well
have been the world's

first multipurpose factory.

It's been described
as the greatest

know concentration
of mechanical power

in the ancient world.

This was an industrial
revolution 2,000 years ago.

Number ten was Caesar's amazing
bridge across the Rhine.

At number nine, the incredible
repeating ballista.

Number eight was the
magnificent Basilica Cisterns.

And number seven,
the intriguing Nemi Tunnels.

Six was the horror that was
the mine at Rio Tinto.

And number five,

astonishing ancient
industry at Barbegal.

But next in our countdown
is an engineering breakthrough

that was bigger still.

It transformed the face
of the towns

and cities
of the Western world.

At number four...

[dramatic music]

Elevating the Romans
to new heights,

it's the ingenious crane,
the polyspastos.

Building in the ancient world
was hugely labor‐intensive.

Every massive block of
the mighty Egyptian pyramids

was hauled up
by manpower alone.

But Roman engineering
was to change building forever.

They invented the ultimate
lifting machine.

‐ The polyspastos was
a massive breakthrough.

It allowed the Romans
to build bigger and faster

than they'd ever done before.

narrator:
This revolutionary machine

was many pulleys joined
together into a crane,

hence the name polyspastos,

meaning multiple pulleys.

The amount that one crane
could lift increased massively

to over 3 tons.

‐ This crane allowed each person

using it to shift 60 times

as much as they would otherwise.

Roman engineering
went into overdrive.

♪ ♪

‐ Incredible buildings
and monuments,

how are they made possible?

With this amazing crane.

♪ ♪

The polyspastos crane
built Rome.

‐ But the Roman engineers
didn't stop there.

They took things
one step further.

♪ ♪

narrator:
The crane's original design

used a capstan
to lift the arm,

which is a horizontal
wheel turned by hand.

But again, the Romans
saw the opportunity

to make their invention
more powerful.

‐ They swapped out the capstan
for a treadwheel,

which was walked by slaves,

thereby doubling the lifting
capacity of the crane.

If you can lift more,
you can build bigger.

♪ ♪

‐ It may be even possible
that several polyspastos cranes

were used together in one big
interlocked mechanism.

And if that's the case,
imagine the lifting power.

The sky is the limit.

♪ ♪

‐ They basically
liked to show off.

Not only did they want to prove

that they had mastery
over the natural world,

they also wanted to
intimidate their enemies.

♪ ♪

narrator: Nothing changed
the face of the empire

as much as
this remarkable crane.

And the monster
lifting machines of today

and the skylines
that they've built

have all evolved from this
groundbreaking device.

♪ ♪

Our next Roman breakthrough
was a monumental

engineering project
at ground level.

At number three...

♪ ♪

The extraordinary and
revolutionary system

of Roman roads.

♪ ♪

Before the Romans,
people used simple tracks,

but the Romans wanted
to march their armies

across their empire,

not to be constrained
by their environment.

They knew a well‐built
and reliable system of roads

would be good for trade,
and for their military.

Road building
went into overdrive.

‐ There are over 250,000 miles

of known Roman roads.

There are probably
actually even more

that we simply don't know about.

That is more

than the distance to the moon.

♪ ♪

narrator:
No civilization since

has ever built on such a scale.

372 great roads connected

the empire's 113 provinces.

‐ In those days, the saying
"all roads lead to Rome"

was more than just a saying.

It was the literal truth.

narrator:
On a newly constructed road,

a Roman legion could march
about 20 miles a day.

The mile itself is
a Roman invention.

It was created to measure
1,000 steps of the army.

The roads were vital for
messengers on horseback too.

‐ On the more important roads
there were post houses.

Messengers could
swap horses here

and ride up to
three times the distance.

That's up to 60 miles every day.

narrator: The Romans created
their roads with precision

and incredibly
modern techniques.

‐ The most amazing thing
about Roman roads

is their construction.

That's what makes them such
incredible feats of engineering.

narrator:
And they were built to last.

‐ There were large stones
at the bottom,

laid up with smaller stones

and then gravel
hard packed on top.

narrator: They're famous
for being straight

because it's
the most efficient way

to reach your destination.

But straight roads were also
a sign of Roman power.

They built them straight
because they could,

whatever the obstacles,

and much of the huge network

can still be seen to this day.

‐ The ingenuity
of their design,

and the sheer amount of mileage

that they covered, means that
the Roman road system

has to have its place
in any Roman top ten.

narrator:
Roads were the glue

that held the Roman Empire
together,

and they still connect
towns and cities today.

♪ ♪

The Romans used
a secret ingredient

in their road construction,

something that transformed
engineering and architecture.

It's a 2,000‐year‐old
technology

that most would think
was only invented

in the past few hundred years.

Next on our list is

an engineering breakthrough

that revolutionized
construction

in the ancient world,

and thousands of years later,

our modern engineering
depends on it.

At number two...

♪ ♪

Is concrete.

‐ Concrete.

The Romans invented concrete

2,000 years ago.

We think of concrete
as a modern discovery.

But in fact, it's reinvention.

It's rediscovery.

narrator: The Pantheon
in the middle of Rome,

one of the most astonishing
buildings ever built.

It's 2,000 years old
and still intact,

and its huge dome

made entirely of
unreinforced concrete.

♪ ♪

‐ The Pantheon was built
as a temple to honor

all of the Roman gods.

It actually has
the largest unreinforced

concrete dome in the world.

The fact that
this is still standing today

just stands as a testament
to the awesome engineering minds

of the ancient Romans.

narrator:
The beauty of concrete

is that it can be poured

and molded into blocks
of any shape.

The Romans could make arches,

vaults, and domes.

This was an architectural
revolution,

and the Pantheon
is the pinnacle

of Roman concrete construction.

‐ The dome of the Pantheon
is a fantastic example

of how good the Romans were

at building in concrete.

It's 142 feet in diameter

with no columns
to support the dome.

That is 50% bigger
than the dome

of the Capitol Building
in Washington.

♪ ♪

‐ The diameter of the Pantheon
is the same

is the height of the structure.

It's an absolutely
enormous space.

You could hold over 5,000
people inside the Pantheon.

It's absolutely amazing.

♪ ♪

‐ Roman concrete technology
was incredible.

In fact,
they varied the densities

of the aggregate in the cement.

They would use
high‐density aggregate

in the foundations
and in the walls,

but then, up in the dome

where the cement had
to be a lot lighter,

they would use
a lower‐density aggregate.

narrator:
It's this ingenious engineering

that allowed the Romans
to build in concrete

without the need
for reinforcement or pillars.

‐ There's one very special
quality of Roman concrete.

It continues to harden
with age.

The dome of the Pantheon
is now stronger

than it was 2,000 years ago.

narrator: Modern concrete
buildings rarely last 50 years.

They are in constant
need of repair.

♪ ♪

The Capitol dome
was finished in 1856

and has had two extensive
restorations since then.

The last time
the Pantheon dome

was repaired was 202 AD,

and that was after
an earthquake.

And there was another
astonishing feature

of Roman concrete.

‐ Roman engineers were so ahead

of their time
that they discovered that

if they changed the chemical
composition of concrete,

this would allow the concrete
to set even under water.

narrator: Underwater concrete,
this was revolutionary.

The key ingredient,

a volcanic ash from the slopes
of Mt. Vesuvius.

‐ It contained about 85%
volcanic ash,

lime, water,

and some even say
animal's blood.

This stuff was strong.

narrator: It doesn't let water
in like modern concrete.

It's weather‐proof,
and resistant to decay,

and incredibly,
it meant that the Romans

could build in the sea
and construct harbors.

‐ They could
build artificial harbors

wherever they wanted.

The Roman Empire flourished.

narrator: The Romans poured
the concrete into wooden
crates,

which then sank into place,

and the concrete
set on the sea bed.

They did this again and again,

building up the harbor,

the concrete continuing
to harden over time underwater.

♪ ♪

The biggest concrete harbor
the Romans built

was at Caesarea
in modern‐day Israel.

♪ ♪

They shipped in 44 ships,

each containing 400 tons
of volcanic ash.

♪ ♪

With concrete, they built one
of the biggest harbors

in the ancient world.

‐ It's over
800,000 square feet.

The harbor at Caesarea rivaled

the finest natural harbors
in the world.

At the time it was constructed,

it was one of the biggest
man‐made structures

to ever exist.

narrator: Caesarea harbor
was 90,000 square yards.

That's big enough to enclose
30 football fields.

It could accommodate 300 ships.

‐ They used over a million
cubic feet of concrete

to build it,

and this thing extended out
into the sea almost half a mile.

It was massive.

♪ ♪

narrator: Concrete was
an engineering breakthrough,

and it has literally
shaped our world

more than any other
ancient invention so far.

♪ ♪

We've seen the most incredible
structures and discoveries,

but there can only be
one number one,

the greatest feat of Roman
engineering of all.

Quite simply, it was the
biggest construction project

the Roman Empire ever undertook

and it was unsurpassed,

not for hundreds of years,
but for millennia.

The greatest Roman engineering
[dramatic music]

At number ten,

we saw Caesar's
incredible bridge,

and number nine was the deadly
repeating ballista.

♪ ♪

At number eight,
the underground cathedral,

the Basilica Cistern,

and number seven,
the extraordinary Nemi Tunnel.

Number six was the horrific
mine that was Rio Tinto.

And then at number five,
Barbegal,

ancient industry.

Number four was the mighty
polyspastos crane.

Number three,
the amazing road system,

and number two,
the concrete revolution.

But what has been picked
as the greatest

engineering feat of them all?

What changed the world
more than anything else?

It's the number one
Rome's Greatest Hit...

♪ ♪

Aqueducts.

‐ Aqueducts were the arteries
of the Roman Empire,

and the Romans
were master engineers

at building them.

narrator: Rome built
its first aqueduct in 312 BC.

It was such a success
that they went on

to build them far and wide.

‐ A marvel of Roman engineering.

Huge networks

transporting gallons
upon gallons

upon gallons of water
across the empire.

narrator:
It's estimated that the Romans

built 6,000 miles of aqueducts,

which if laid end to end,

would go 1/4 of the way
around the world.

♪ ♪

A ready supply of fresh water

meant that Roman
civilization could flourish.

Agriculture, industry,
and expansion of the empire.

‐ They could establish
cities in places

that they otherwise couldn't

because they wouldn't have had a
secure supply of drinking water.

narrator:
All across the empire,

a supply of fresh water

meant that cities
could grow and prosper.

♪ ♪

The main aqueduct
supplying the city of Rome

was an incredible
57 miles long,

but this wasn't
the only one.

‐ Eleven aqueducts totaling
more than 300 miles in length.

That's 183 Golden Gate Bridges.

♪ ♪

‐ In total,
over 300 million gallons

of water flowed into Rome
each day.

That's more per person
than modern day New York City.

narrator: Enough for
drinking water, sanitation,

bath houses,

and even the occasional
spectacular event

on an epic scale.

‐ One of the most remarkable
engineering feats

associated with the Colosseum
is for the inaugural games,

they actually flooded
the arena floor

for naval battles,

and the next day
had it all drained out,

and the stage back in place.

♪ ♪

Incredible.

narrator: Just as amazing
is the precision engineering

that went into Roman aqueducts,

and none more so than
the Pont du Gard

in Southern France.

‐ This thing is huge.

16 stories high.

164 feet.

It's the height
of the Colosseum.

Enormous.

It's made of over
50,000 tons of stone,

and it's still standing.

♪ ♪

‐ The bridge over
the gorge covers

just a small section.

The whole aqueduct actually
travels for 30 miles.

Even today, that would be
a public works undertaking

on an unimaginable scale.

♪ ♪

narrator:
The precision engineering

that went into Roman aqueducts

like Pont du Gard
is incredible.

‐ The wow fact that stays
in my mind

is that over the course
of the whole aqueduct,

that's 30 miles,

the drop in height
is only 55 feet.

That is an absolute tour
de force of Roman engineering.

narrator: The gradient
is less than 1%,

imperceptible to the naked eye.

‐ With a one‐foot drop
every 3,000 feet,

the rate of flow was
58 gallons per second.

That's pretty amazing.

narrator:
And there was yet another

technological innovation
that was

way ahead of its time,
the inverted siphon.

As long as one side
is slightly lower,

water flows from one pipe down,

then up to the other.

It meant that no valley
was too wide to cross.

‐ The inverted siphon,
ingenious.

Not only could water
be transported

along level ground
and downhill,

but thanks to
this innovation,

they could transport
water uphill.

narrator: When this principle
was applied to huge aqueducts,

the Romans could transport
water no matter the terrain.

There could even be
a series of these tanks

from one valley
to the next.

‐ The Romans perfected
the inverted siphon technique,

and they rolled it out
across the entire Empire.

In any one hour, they could

make 10 million gallons
of water flow.

Not just flow, it flowed uphill.

narrator: An infrastructure
project on this scale

had never been tried before.

It hadn't even
been contemplated.

‐ But that's what
the Romans were like.

They'd come up with
the most amazing solutions

no matter how crazy
or ambitious the plan.

♪ ♪

narrator: Aqueducts were the
veins of the Roman Empire.

Their civilization
depended on them.

The world hasn't seen
engineering on this scale
since.

♪ ♪

Roman engineering was
the greatest

of the ancient world.

It overcame
any obstacle in its way

centuries ahead of its time.

It transformed the Roman world,

and in doing so,
it has transformed ours too.