Leaning Tower of Pisa

The Leaning Tower of Pisa is the campanile, or bell tower, of Pisa Cathedral, standing in the Piazza del Duomo, also known as the Piazza dei Miracoli, in Tuscany. Work began in 1173, and the tower took nearly two centuries to complete, with the bell chamber finished around 1372. The architect of the first stages is uncertain; Bonanno Pisano and Diotisalvi are among the names traditionally linked to it.

The tower began to lean after the second floor was built, because its shallow foundation sat on soft ground of clay, sand and shells. Wars with Genoa and Florence halted construction for long periods, which allowed the soil to settle and probably saved the tower from collapse. Later builders tried to compensate by making the upper floors slightly taller on the lower side, which gives the tower a gentle curve.

The tower is about 56 metres tall on its lower side and is built of white and grey marble. It has eight levels, including six open galleries of arches, and a staircase of 294 or 296 steps, depending on the count, winds up inside the walls to the bell chamber, which holds seven bells tuned to a musical scale. By 1990 the tilt had reached about 5.5 degrees, and the tower was closed for stabilisation work that removed soil from under the higher side. When it reopened in 2001 the lean had been reduced to about 4 degrees.

The tower is part of the Piazza del Duomo ensemble with the cathedral, the baptistery and the Camposanto cemetery, inscribed together as a UNESCO World Heritage Site in 1987.

Climbs are by timed ticket in small groups with a guardian, and the number of visitors on the stairs at one time is limited, so booking ahead on the official Opera della Primaziale Pisana website is advisable in busy months. Bags must be left at the cloakroom before climbing, and young children are not allowed up.

How was the tower saved?

The tower closed to visitors in 1990, and engineers worked on it from 1993 to 2001, slowly extracting about 70 tonnes of soil from beneath the raised north side so the structure could settle back. It reopened on 15 December 2001, and in May 2008 engineers reported that it had stopped moving for the first time in its history, with stability expected for at least 200 years.

The weight the soil has to carry is about 14,500 tonnes. At its base the tower measures 15.48 metres across on the outside, and the walls there are 2.44 metres thick, which is why the staircase can spiral up inside them.

Each of the seven bells has its own name and date. The oldest, La Pasquereccia, also called La Giustizia, was cast in 1262, and L'Assunta in 1654. Dal Pozzo, first cast in 1606, was recast in 2004. The tower's best-known story concerns Galileo, who was born in Pisa. Between 1589 and 1592 he is said to have dropped two balls of different mass from the top to show they fell at the same speed. The account comes from a biography by his pupil Vincenzo Viviani, written in 1654, and historians treat it with caution.