Why Is the Leaning Tower of Pisa Leaning?

Soft soil and uneven settling

The tower is the freestanding bell tower of Pisa Cathedral. The lean became apparent in the late 1170s, after three of its eight stories were completed, caused by uneven settling in soft ground. Construction had started in 1173, and when the third floor was built the tower had already bent 5 cm to the southeast.

The name of the city hints at the problem. Pisa got its name around 600 BC from a Greek word meaning marshy land, so the ground under the square has been soft for a very long time.

Builders made the lean worse

Later builders tried to correct the tilt by making the new stories slightly taller on the short side. Giovanni di Simone used this trick, and it backfired: the added weight on one side made the tower sink further. That is why the tower has a slight curvature, a gentle banana shape rather than a straight tilt.

What the engineers did

Between 1993 and 2001, teams removed soil from beneath the foundations rather than propping the tower up, letting it settle back gently. The work was completed in May 2001 and cut the tilt to 3.97 degrees.

Sensors showed the motion had stopped in 2008, with a total improvement of 19 inches. Before the repair the tower had been tilting about 2 millimetres per year, and there has been no measured movement since 2008.

Is it possible to straighten the Leaning Tower of Pisa?

Full straightening was never the goal, because the lean is why millions come. Engineers instead reduced the tilt to a safe angle while keeping the character of the building, and they expect it to remain stable for at least 200 years.

Will Pisa ever fall

All the signs point to no. Sensors confirmed the movement stopped in 2008, and the engineers behind the stabilization project expect the tower to stay standing for at least 200 years. The tower survived centuries of soft-ground creep and earthquakes before any modern intervention, so its current state is the most stable it has been in living memory.

One curiosity backs this up: even the flagpole on top is vertical rather than following the angle of the tower below, a small marker of how precisely the structure is monitored.

Why is it important

Piazza del Duomo, Pisa was inscribed on the UNESCO World Heritage List in 1987, covering 8.87 ha with a 254 ha buffer zone, under criteria recognising the cathedral, baptistery, bell tower and Campo Santo. UNESCO also notes that Galileo observed a swinging bronze chandelier in the cathedral, which fed his early work on dynamics. More than 5 million people visit the tower each year.

One surprise: Pisa does not hold the world record. The most inclined tower in the world is the bell tower of Suurhusen in Lower Saxony, at almost 5.07 degrees, more than Pisa's 3.97 degrees.

Myth two, it was built to lean

No builder wanted a leaning bell tower. The tilt appeared by accident in the late 1170s because of the soft ground, and every later attempt to hide it only shaped the tower's curve. The lean is a flaw that became the attraction.

Visiting with kids or a guided trip

Children under 11 with an adult enter the Cathedral, Baptistery, Camposanto and the two museums free without a ticket, so the square is workable for families even if the youngest cannot climb. If you want the climb, transport and timing handled for you, a guided pisa tours from florence package covers the whole day.

By bus or on a tour

Autolinee Toscane's urban single ticket for Pisa costs €2.00, or €3.00 bought from the driver, according to the operator's ticket page. The simplest option is a guided half-day tour that does the driving for you and drops you close to the square.