Leaning Tower of Pisa

Interesting facts

The tower holds seven bells tuned to a musical scale; the oldest, La Pasquereccia of 1262, once rang to announce executions.

Its largest bell, L'Assunta, was cast in 1654 and weighs about 3,620 kilograms.

Building took 199 years in three stages: the foundations went in on 9 August 1173 and the bell chamber was finished in 1372.

The foundations go down only about three metres, which explains why the tower began sinking once the second floor was reached in 1178.

The whole structure weighs roughly 14,500 tonnes, and its walls are about 2.44 metres thick at the base.

Climbers count 296 or 294 steps to the top, because the seventh floor has two fewer steps than the others.

Before soil was drawn out, engineers stacked some 870 tonnes of lead counterweights on the raised side starting in 1993.

About 70 tonnes of earth were removed from beneath the tower, returning its lean to where it stood in 1838.

In 2008 surveyors confirmed that the tower had stopped moving altogether for the first time in its history.

Who designed it is still disputed: a 2001 study pointed to Diotisalvi, architect of the nearby Baptistery, rather than Bonanno Pisano.

Why it is worth it

The tower started leaning almost as soon as it was built, and everyone building it noticed. Construction began in 1173, traditionally credited to Bonanno Pisano though historians still argue over the attribution, and by the time masons reached the third of eight planned stories, the soft ground beneath — a mix of clay, sand, and shell fragments — had already begun settling unevenly. Work stopped outright rather than risk the structure.

What saved the tower may have been sheer bad luck elsewhere. War broke out between Pisa and Genoa and halted construction for nearly a century, and that century of inactivity let the compromised soil gradually compress and stabilize under the tower's existing weight rather than collapsing under ever more of it. When building resumed in 1272 under Giovanni di Simone, his workaround wasn't to fix the lean but to compensate for it: he built the remaining stories slightly taller on the low side, which is why the tower isn't just tilted but subtly curved, like a soft banana, rather than a straight leaning cylinder.

By the twentieth century the lean had crept past 5 degrees and engineers judged the tower at real risk of toppling. It was closed to visitors for roughly a decade starting in 1990 while crews carefully extracted small amounts of soil from beneath the raised north side, coaxing the whole structure back by about 44 centimeters — enough, by current estimates, to buy it several more centuries, with no intention of ever making it stand perfectly straight.

Good to know

Around 3.2 million people visit each year; entry to climb the tower is limited to small timed groups because the interior spiral staircase is narrow.

Getting there

Located in Pisa. Pisa International Airport (PSA) is about 4 km away.

From the encyclopaedia

The Leaning Tower of Pisa, or simply the Tower of Pisa, is the campanile, or freestanding bell tower, of Pisa Cathedral. It is known for its nearly four-degree lean, the result of an unstable foundation. The tower is one of three structures in Pisa's Cathedral Square, which includes the cathedral and Pisa Baptistry. Over time, the flawed tower has become one of the most visited tourist attractions in the world as well as an architectural icon of Italy, receiving over 5 million visitors each year.

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