Construction of the Leaning Tower of Pisa began in 1173 and lasted almost two centuries. The tower was originally intended to be a free-standing bell tower for the nearby cathedral, but as construction progressed it became apparent that the tower was leaning to the southeast due to unstable soil and poor foundations.

The tilt of the tower was caused by a combination of factors. The tower was built on soft soil consisting of clay, fine sand and shells, which caused the foundation to sag unevenly and over time the tower tilted. In addition, during construction, the builders used a weak, unstable mortar, which contributed to the tilt of the tower.

Despite the gradual tilt, the tower did not fall for several reasons. First, the tower's shallow foundation prevented it from completely toppling over. Additionally, the soft soil beneath the tower acted as a cushion, absorbing some of the weight and pressure of the sloping structure. Finally, attempts to straighten the tower in the 20th century, such as removing soil from the higher side and installing counterweights, helped stabilize the tower and prevent it from leaning further.

Today, the Leaning Tower of Pisa remains a popular tourist attraction and a testament to the ingenuity of its builders and the unpredictability of nature.