You're walking along the main street in a town that you have not visited before. Suddenly you stop dead in your tracks: there's a building up ahead you that you cannot believe exists.
It looks impossible, but you rub your eyes to make sure you're not dreaming.
The building is leaning at a very dangerous angle. Buildings do not lean! They stand up straight otherwise they would fall over.
But then you remember where you are. You are in the Italian town of Pisa and you are looking at its famous leaning tower.
Nobody knows how long The Leaning Tower of Pisa will continue to lean before it collapses. Architects and engineers are always coming up with schemes to stop the tower falling over, but no one has yet found an answer to the problem.
The tower stands 54 metres high and now leans 4.5 metres out of true. It was begun in 1173 and finished almost two hundred years later in 1350. It was built to house the bell that rings to call the citizens of Pisa to worship in the cathedral next door.
