The story of Leaning Tower of Pisa

On 9 August 1173 the foundations of this bell tower were laid, just three metres deep in weak, unstable soil. By 1178, when building had reached the second floor, the tower had already begun to sink. Then work stopped for the better part of a century while Pisa fought Genoa, Lucca and Florence, and that pause let the soil settle; otherwise the tower would almost certainly have toppled.

When construction resumed, the builders made the upper floors taller on one side to compensate, which is why the tower is actually curved. The bell chamber was added in 1372, with seven bells, one for each note of the major scale. Galileo Galilei is said to have dropped two cannonballs of different masses from here to show that they fall at the same speed.

By 1990 the tilt had reached 5.5 degrees; work between 1993 and 2001 reduced it to 3.97 degrees. Today the tower receives over 5 million visitors a year.