The Assassin (Sha ren zhe Tang Zhan)

Today on "Impossible engineering,"

the Millau viaduct, the tallest bridge on earth...

Rising 1,000 feet over one of Europe's deepest valleys...

Built on pioneering innovations from the past...

All right, now, this is what I'm talkin' about.

Today, the stromsund bridge is

a real landmark breakthrough in the world of engineering.

...To make the impossible possible.

captions paid for by Discovery communications

Nestled in the Southern corner of the massif central in France

is the tranquil medieval town of Millau.

But every summer, that tranquility is shattered.

Millau lies directly in the path of the busiest travel route

between Paris and the mediterranean coast.

To free Millau from this plague of traffic,

engineer Michel Virlogeux is attempting

what was previously thought to be impossible...

build a road high above Millau

across the gargantuan Tarn valley.

The result...

the Millau viaduct,

the tallest bridge on earth.

This massive bridge spans a staggering 1 1/2 miles,

towering over 500 feet above the Tarn valley.

Just seven concrete piers support

the 40,000-ton steel deck,

which is held in place by a single row

of 154 super-strength cable stays.

Michel had to design a bridge that could span

one of Europe's deepest, widest, and windiest canyons,

using an uneven valley floor as a foundation.

To build the tallest bridge on earth,

Michel and his team need strong building materials,

something that would be impossible

without help from the great innovators of the past.

Man's earliest building materials were sourced

from nature.

Neanderthals built shelters from the bones

and tusks of wooly mammoths.

Mongolian nomads used sheep wool

to line the walls of their yurts.

And from the time of ancient civilizations,

many houses have been built with straw and clay bricks...

Reinforced with a touch of animal dung,

which works perfectly...

as long as you're standing in the right place.

To create a truly enduring structure,

engineers at Millau would look to the achievements made

by a British civil engineer 250 years ago.

Professor Luke Bisby is heading out into the English channel

to visit what's left of a truly revolutionary structure.

I'm heading out to the Eddystone,

one of the most treacherous rocks

in the English channel.

It's a place that arguably marks one of the most important

moments in civil-engineering history.

Today sits a 50-meter-tall lighthouse

designed by James douglass in 1882.

Amazingly, this is the fourth lighthouse

that's stood in this spot.

Eddystone rock is 14 miles from the busy port of Plymouth.

The rock has sunk countless ships

over the centuries.

In the 17th century,

a lighthouse was built to warn passing vessels.

A building that could withstand

the elements out here, the pounding of the waves

day after day and the wind and the rain,

requires a real engineering achievement.

In 1696, Henry Winstanley built

the world's first offshore lighthouse.

It was an 82-foot wooden tower.

But just 7 years later, it was obliterated by a storm.

Its replacement survived 47 years.

But that too was destroyed by the elements,

this time by fire.

If a lighthouse was gonna last any substantial amount of time

out here, a new engineering solution was needed.

Engineer John Smeaton had a unique idea

for the Eddystone lighthouse.

He believed that the sea must give way to the building

and decided to build a lighthouse made of stone.

It was how Smeaton joined the stones together

that was truly revolutionary,

earning him the title

"the father of civil engineering."

Smeaton's original lighthouse stood on this spot

for over 120 years.

And, in fact, we can still see the bottom half of it

as that stump of a lighthouse over there.

Smeaton's structure was so strong,

it was only cracks in the rocks that it sat on

that forced engineers to dismantle the lighthouse

and rebuild it on Plymouth hoe.

The secret to Smeaton's success is

an innovative bonding material that can survive

the constant pounding of the sea.

Smeaton experimented with mixtures of lime,

Clay, and iron slag to create hydraulic lime.

I'm gonna try to demonstrate the innovation

that Smeaton accomplished at the tower.

Here we have a traditional cob mortar.

This is a mixture of sand and clay and straw

and lime and a bit of earth.

And these types of mortars were used traditionally

for many hundreds and thousands of years.

And the other material that I have here

is Smeaton's mixture.

Luke places Smeaton's hydraulic lime

inside a cardboard tube,

then places the tube in water.

And then I'm also gonna do the same

with the traditional earth mixture.

Got both tubes now filled with the mortar.

We're gonna go away for about a half an hour.

And then we're gonna come back, and hopefully, we'll see

a pretty dramatic difference

in terms of how they've performed.

First, we're gonna look at the tube that's filled

with the traditional mud mortar.

We're gonna see exactly how much it's set.

And you can see... absolutely nothing.

This is the one we're much more interested in.

This is the one with the mortar

that's based on the hydraulic-lime technology

that Smeaton came up with.

I can immediately feel that this one is much more solid.

I squeeze it. Nothing happens.

If I have a look inside,

I can actually see this now is very, very solid.

That combination of setting very quickly

and setting underwater completely revolutionized

civil engineering.

What Smeaton had created

was the precursor to Portland cement.

Portland cement's the key ingredient

in all modern concrete.

The strength of Smeaton's hydraulic lime

allowed engineers to stack nearly 1,500 blocks of granite,

creating a rock-solid structure that could stand up

against the forces of nature...

so solid, in fact, the victorians couldn't

dismantle the base when the lighthouse was relocated

to Plymouth hoe over 100 years ago.

So here we have the original 250-year-old granite blocks

re-assembled here on Plymouth hoe

with mortar much like the original mortar.

Incredible that it still looks so good.

And if I look really carefully,

way out there on the horizon,

I can just see the base of Smeaton's original tower

standing next to the new tower.

This was really the game-changer

in concrete engineering worldwide.

The engineers at the Millau viaduct

are using John Smeaton's hydraulic-lime technology...

On an epic scale

...To build seven of the tallest bridge piers

on the planet.

The Millau viaduct, soaring high

above the French countryside...

it's the world's tallest bridge.

To support this engineering marvel,

its designers had to construct

seven of the tallest bridge piers on earth.

Chief engineer Michel Virlogeux had

just 4 years to finish the bridge

or face fines of up to $30,000 per day.

So, to save time, each pier was built simultaneously

at seven individual work sites.

Due to the uneven valley floor,

each pier is constructed at a different height,

the tallest a record-breaking 804 feet.

Their octagonal shape tapers gradually,

splitting around 300 feet below deck height

for added flexibility.

Engineers built each pier in 13-foot sections

using a self-climbing frame.

A hydraulic-driven system pushed the giant concrete mold

up in stages.

Cranes lift buckets of concrete,

which is then poured into the concrete mold.

After each pour has set, the mold is dismantled.

The frame carrying the mold

is then mechanically pushed by the hydraulic Jacks

up the piers

and re-anchored in the set concrete.

The mold is then re-assembled for the next pour.

Each cycle takes about 3 days.

The piers are completed ahead of schedule,

in just over 2 years.

With the bridge piers complete, Michel is ready to tackle

his next challenge...

construct Millau's 1 1/2-mile-long bridge deck,

long enough to span the vast Tarn valley...

...creating even more impossible engineering.

The Millau viaduct in southwest France

is an engineering wonder of the modern world.

At 1,125 feet, this superstructure stands taller

than any other bridge on earth.