The Leaning Tower of Pisa is the freestanding bell tower (a campanile) of the Cathedral of Pisa (Duomo di Pisa). The tower is one of the components of the Piazza dei Miracoli. The architects were Gugilmo and Buonanno.

Shortly after construction began in 1173, the tower began to lean. Because construction continued perpendicularly, the tower is not only crooked but also warped.
The tower is 55.85 meters high and weighs an estimated 14,453 tons. The current slope is about 10%. The tower has 297 steps.