Discovery On the Inside The Leaning Tower of Pisa

It's a marble masterpiece,

one of the most famous buildings in the world.

The Leaning Tower of Pisa is simply an impossibility.

More like something you dream than something that can exist.

For hundreds of years, the world has watched in amazement

as the building defies gravity teetering on a razor's edge.

It really is quite miraculous that it has not fallen over.

And thank goodness it hasn't.

If the Tower were to fall no one would feel it

more than the people of Pisa.

For them the Tower is the heart of their city.

It is what draws hundreds of thousands of tourists every year,

each one anxious to give a helping hand.

It really needs one. The Leaning Tower of Pisa can tumble

in an instant.

For 800 years architects and engineers have been trying to

fiix the Leaning Tower of Pisa.

Nearly every attempt has been disastrous.

But somehow the Tower has serenely survived.

Today the Tower is in greater danger than ever.

It's lean is so extreme

that the Italian government has closed it to avoid a potential disaster.

It's been more than ten years since anyone has walked up its marble

stairway which leads to its stunning bell chamber

until now.

We will take a behind the scenes look inside the Tower

that's been locked off to the public for so long

and climb to the top for a rare view of its breathtaking vistas.

We'll examine the bizarre history of the 800 year effort to

save the Tower and introduce the current plan that some believe

just may make the Tower safe forever,

that is if it doesn't destroy it first.

Today, the Tower is in crisis a patient in intensive care.

830 tons of lead have been added to hold down its north side.

Steel bands cinch its waist.

340-foot long cables are wrapped around it to prevent

an impending catastrophe,

while a group of international experts struggle to fiind

a permanent solution.

Michele Jamiolkowski a geo-technical engineer

is the chairman of the current team to save the Tower.

This is not an easy task.

Not only me, but all the other members of the committee

became acquainted with the responsibility and with the risk

which we are incurring with this task.

Their goal is to reduce the Tower's lean by about 16 inches.

This would take the Tower out of danger, but keep it looking the same.

After all, no one wants a straight Tower of Pisa.

We never considered straightening the Tower, because the inclination

is part of its character.

It's absolutely central to Pisa.

So there are two unacceptable scenarios really, aren't there?

One would be a straight Tower but the other one would be

one that fell over.

The common perception is that the Tower is in danger of tipping over.

In fact, that is only one of two perils that could reduce it to rubble.

One problem is the very well known continuous increase of inclination,

which was bringing the Tower to falling over.

And the second problem was the concern about the structural collapse.

The first problem, the Tower's increasing slant is due to the soft

soil it is built on.

Professor Carlo Viggiani is a member of the committee to save the Tower.

He has been studying the Tower for over 35 years.

The leaning was by change. Probably because on the south

side of the Tower

the subsoil was weaker than the north side.

So, and once it started to lean from that side, then the weight is

going on that side

and the thing is continuously increasing.

By 1990, the Tower was leaning at an astounding five

and a half degrees,

or 17 feet off the perpendicular.

It literally defies the laws of physics.

Committee member John Burland is a professor of soil mechanics.

I think it's miraculous.

I mean, when we came here in 1990,

we couldn't get it to stand up on our computer.

It's leaning at 5.5 degrees. We could only get our computer

Tower to lean at 5.44 degrees and then it used to fall over.

So it really is quite miraculous that it has not fallen over.

The Tower isn't just in danger of falling,

it can collapse under its own weight.

Part of the problem stems from its structure.

Although the Tower appears solid,

it's actually a hollow cylinder reaching 185 feet into the sky.

Within it, a staircase winds up to the top.

Most of its 14,000 tons are supported by its walls.

Its walls, however, aren't solid either.

They're stone, lime and mortar, covered with a thin marble facade.

One side with all of the stone is getting a lot of pressure.

The other side with all of its stone is not getting that pressure,

so there is an inequality.

As the Tower's lean continues the pressure intensifies.

Eventually the marble in this second floor section

will give way the building will collapse upon itself.

It could explode at any time, or this was the case in 1990 anyway.

So we've got a Tower that's just about to fall over and it's

on the point of exploding.

And that makes it probably the biggest civil engineering

challenge there is.

Solving the challenge of the Tower has stumped

generations of engineers.

Its problems began almost as soon as it was built.

When plans for the Tower were first drawn up in the 12th Century,

a spot was chosen with a commanding view of Pisa.

It was beautiful.

But not a very good place to build,

since in ancient Italy the site had been a lagoon.

Piero Pierotti, is an art historian and professor of medieval architecture

at the University of Pisa.

Pisa was a system of islands in the middle of a very wide lagoon.

This lagoon was slowly filled in by the two most important

Tuscan rivers. The Arno and the Auser.

And where the rivers had filled in, they left mud,

which is softer and wet.

The soft wet soil left behind by the rivers was where the Tower was built.

The ground is so soft that it's really like building a brick Tower

on a soft carpet.

You can go to a certain height,

and no matter how straight you try and keep that Tower,

it will start to lean and then fall over.

Why build a Tower doomed to lean?

Although the medieval architects knew that the soil was soft,

they may not have known how soft.

They thought they had found the perfect spot to build a monument

to the glory of Pisa.

Today, Pisa is a quiet university town of 100,000.

In the 11 th Century, it was a powerful city-state.

Its navy roved the seas conquering other cities.

In 1062, the Pisa navy sailed to Palermo, the capital of Sicily,

bent on conquest.

When Pisa's fleet arrived in Palermo...

the Sicilians they encountered there said that the citizens of Pisa

were the meanest and most ignorant people they had ever met.

In reality, there was this strong arrogance of considering

themselves the first, the best.

This arrogance made it easy for other cities to fiind allies against Pisa.

In 1063, the victorious Pisan navy returned,

their chests bursting with pride and their pockets bursting

with Sicilian money.

They decided to build a glorious square, the religious center

of medieval Pisa,

the square known today as the Piazza dei Miracoli,

Square of Miracles.

It would have a magnificent cathedral, one that would surpass

any other church in Italy.

Next to it would be a baptistery where Pisa's richest citizens

could be baptized.

It's crowning glory,

the masterpiece of Pisan civilization would be the cathedral's bell Tower,

or campanile.

On August Ninth, 1173, the foundation for the Tower was laid,

directed it is thought, by Pisan architect, Bonnano Pisano.

By the time the third level was built the Tower was starting to

settle unevenly.

It was leaning north not south as it does today.

The Italians weren't worried.

Many buildings in Pisa leaned a little.

They simply compensated

by making the columns and arches on the north side of the third

level a little taller.

Pisa had something like 10,000 towers.

It was known that an adjustment of the ground was necessary.

They would start construction and they would look onto

which side the Tower was leaning

and would build up the other side.

They didn't have the technology which we have now.

If we were doing the Tower now we would have driven

what are called piles

down onto that dense sand 40 meters down.

But they didn't have that technology in 1173.

They just learnt that you could build towers to a certain height

from years and centuries of experience.

But what they had learned from experience,

did not hold true for this Tower.

The soil here was softer and the Tower would have fallen

if they continued building.

But they didn't.

In 1178, construction stopped.

Some historians say it was because the Tower was tilting too much.

Others say it was political and military troubles in Pisa.

Whatever the reason, the delay lasted 100 years.

The Tower survived only because the interruption allowed

the soil beneath the Tower

to settle to include the resistance and to support the fiinal

lot of the Tower.

When work resumed in the 13th Century the Tower was leaning

about seven inches to the north. As building continued upwards,

the Tower began to tilt in the opposite direction.

This time, the masons tried to correct the tilt by making the stones

on the south side taller.

They corrected the shape just to bring the Tower in a vertical position

so that the Tower is not actually straight.

It is like a banana. It is shaped in this way.

In 1278, work on the Tower stopped just short of the fiinal floor.

82 years passed before architect Tomasso Andrea di Pisa came

on to build the bell chamber.

By 1370, the Tower was complete and the original vision of the great

square with its Tower was realized.

But as soon as the Tower reached its full height,