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Why does the Tower of Pisa lean?

Looking at it, you feel it is going to fall any minute… and yet, it’s been there for centuries, charming tourists with its peculiar tilt: it’s the Leaning Tower of Pisa, one of the most unique monuments in the world.

Characteristics

The tower is about 56 metres high and was built between the 12th and 14th centuries.

Inside there are two rooms, both without a ceiling. One is located at the base of the tower and is known as Sala del Pesce (“Room of the Fish”) due to a bas relief portraying a fish. The other is on the seventh floor and constitutes the belfry. It is possible to see the tower’s ground floor thanks to an opening at the center and to go to the top by climbing three flights of stairs.

Origin of the tilt

The Tower of Pisa, built on sand-clay soil, started to lean when construction on the third floor began. Construction was stopped and resumed years later, building the remaining floors with a curvature opposite to the tilt. This confirms that the tower was never straight, as even the lower floors were tilted.

It has been ascertained that the cause of the tilt is the weak composition of the soil; being soft and of alluvial nature, it can’t support heavy weights.  After all, other buildings in Pisa lean as well, creating an extraordinary ensemble of buildings, churches, and bell towers all leaning in different directions.

Will the Leaning Tower fall?

“The tower that leans, that leans, that will never come down,” says an old Pisan saying. But is it true?

In the last decades of the 20th century, the tower suffered a major increase of the tilt angle, which made for a concrete danger of collapse. Thanks to works of strengthening lasting from 1990 to 2001, the tilt of the belfry has been reduced, bringing it back to the level of two centuries earlier.

In March 2008, the tower reached the final level of strengthening, with a tilt of almost 4 degrees. According to the experts, this will keep the tower safe for at least three more centuries, allowing visitors to access one of Italy’s most representative monuments.