Why does the Leaning Tower of Pisa lean?

The Leaning Tower of Pisa is an eight-storey tower that has become one of the world’s most famous tourist attractions. However, you probably won’t be surprised to learn that it wasn’t intended to be famous for its unique gradient.

Leaning_tower_of_pisa_2Building started on 9 August 1173 but the workers made two key errors. Firstly, they made the foundations a mere three metres deep, which is not deep enough at all for a building of that size and weight. Secondly, they built the tower on ground consisting of clay that was much too weak to hold the structure.

Realising that the tower was beginning to lean as part of it sank into the clay, building stopped for nearly 100 years, only beginning again in 1272 when Giovanni di Simone thought he had found the solution. He hadn’t. The tower leaned even more despite his efforts to rebalance it and they stopped again 12 years later. It was finally finished in 1372.

Between 1990 and 2001 the tower was closed so workers could straighten the tower slightly and make it much more secure and safe.