They do lead.

But the Leaning Tower of Pisa just looks like it's defying the lower Felix.

And that's all to do with its center of mass, which is just about yeah, experts calculate the towers Center of Mass is around the fourth floor.

As long as this sits above the base of the building, it will stand.

But if it moves outside of that area, you have a disaster.

Calculations show the wind tower was a lean of about 5.44 degrees.

It should have collapsed by 1998 was already 5.5.

It should have gone down.

No one knows why it didn't collapse.

With so many rescue efforts over the centuries, the calculations of the lean have become confusing.

To make matters worse, the lean compounds an issue hidden in the walls that could take the tower out before the lean knocks it over.

The greatest danger for the Tower of Pisa has not been that it should simply fall over because of its wait.

There are other dangers as well, one of which is the incredible amount of stress which is produced on certain areas of the tower due to the weight of the tower.

Tilt strains the walls, which can be devastating to a structure built from solid stone.

But while these look solid walls air filled with a random mix of building materials, making them less sturdy, there has been a great concern that the tower would rather a burst and implode rather than topple over.

No only could the tower of fooling it could have exploded at any point.

It defies belief that it's still standing.

After decades of discussion, design and prototyping.

In 2003 go ahead to build the barrier was finally given.

Aim of this ambitious project was to divide the Venetian lagoon from the Adriatic Sea by placing barriers across three inlets.

A total of 78 mobile gates needed to be laid at the bottom of the sea bed.

Each one is 28 meters long, 20 meters wide and weighs a colossal 300 tons.

Mostly consists of a series of gates that lie flat on the seabed and their hinged at one end and to activate them, air is pumped into the gates, and through the principle of buoyancy, the gates rise up, providing a barrier between the Venetian lagoon on the Adriatic Sea.

The design was revolutionary and would allow authorities to open and close the sea gates to cope with title surges of up to 2.7 meters.

At least that was the plan.

But to match the biblical scale of this project, the catalog of catastrophes has been almighty as well, becoming a joke amongst Venetians.

So what they didn't think about was that when the barriers up tidal forces come push sand and silt underneath the barrier so it can't sit back down properly.

Engineers realized that when the gates were raised, sand would settle in the trenches, which meant that when the gates were shut, they couldn't close.

Probably materials used in the construction of the barrier have already shown significant signs of wear.

Another really difficult problem is corrosion.

The gates that were installed underwater are already showing huge signs of corrosion, and gates that haven't even been put in yet that are on the land are starting to rust.

So this is going to render them much, much weaker and can lead to huge mechanical failures in the future.

Barriers are made out of these big metal panels and that pain is being corroded.

That's also something that you know is a well known feature of salty water.

The gate, sir corroding even the replacement gates a corroded.

Clearly, they chose materials that just couldn't withstand saltwater and sea air.

To add insult to injury, a tiny Venetian resident is causing huge extra problems.

What they didn't also think about was the environment department of See.

There's lots of muscles and all sorts of creatures down there.

They start to live on the brackets on the hinges, meaning that sometimes these hinges or inoperable.

There was some issue with the hinges, and lo and behold, there were muscles growing on the hinges.

And the only way to deal with that is toe have divers go down and literally scraped them off, which just seems ridiculous.

By the late seventies, having failed to prevent the fire from spreading closer to the town, residents were worn that Centralia was unsafe.

Most people stayed put until a dramatic event convinced them of a very real danger.

When co seems burned on the grounds, they undermine the integrity of the surface.

Frighteningly, this can result in sinkholes opening up, revealing the burning coal below.

That's exactly what happened on Valentine's Day 1981 when a young Todd Dombrowski was exploring his grandmother's backyard.

Right now is standing in front of the home of Todd them basket, a young 12 year old boy that fell into the sinkhole, not saying call was in the backyard, which tried to get to it.

All these brambles stuff here, but it was about 30 feet back on the right.

He saw a puff of steam coming out at the base of the tree, so he went over to see why.

And when he got there, the grandest went out right from under me and opened up on steam.

Shot about 50 feet, dear.

Miraculously, the boy was hauled out by his cousin and survived.

Eventually, it attracted all new major news media in the country on the world.

Really usually a mind fire didn't cause too much attention before, but that that shone a spotlight on it.

Andi, the end result was what you see now.

Everybody left by chance.

State politicians were visiting that day and witnessed the aftermath.

They insisted that the state intervene, But with the underground fire now so huge extinguishing it was no longer a viable option.

It was Centralia.

It was just finally a matter of money.

What's gonna cost more to take this huge barrier and surrounded Cole?

Just about everybody out.

So they decided to buy everybody up is a cheaper alternative.

I think it was 42 million in supposed to $200 million to do that remediation operation Government offered residents a substantial cash sum to leave.

But despite the cracking highways, noxious gases and sudden single, many people in Centralia were still reluctant to abandon their homes.