The Leaning Tower of Pisa

What is it?

The bell tower of the small Italian city, Pisa. The footings for the tower were originally only 3m deep and the soil upon which they were founded was very weak, dropping under one side of the tower and causing its globally famous lean. Construction of the tower took place across 177 years and 3 stages, beginning in 1173.

Subsidence in the soil was noticed as early as the first stage of construction, when only the ground floor of the tower was finished. Fortunately, Pisa became distracted by a series of conflicts with surrounding towns, halting construction for a century or so and inadvertently allowing the soil to settle and stabilise. The lean was there to stay however. Giovanni di Simone, the architect for the second stage of construction, went so far as to design the upper floors of the tower with one side taller than the other in an effort to compensate for the lean. As a result, the tower is slightly curved along its height.

First seen in an article on World Architecture News, here, the tower has been in the news recently after the removal of scaffolding that has surrounded various parts of the tower for the past 20 years. After almost AU$40m of stabilisation and painstaking restoration works, the tower is once again fully open to the public.

What do we think?

The various efforts at stabilisation that have taken place over the years are a story in and of themselves: in 1964, 800 tonnes of lead weights were added to the raised side of the tower’s base to counterbalance the soft soil; in 1987, the heavy bells were removed from the tower, post-tensioned cables were tied around the 3rd storey and anchored to the ground, and 38 cubic metres of soil were removed from the tower’s base.

All up, considerable expense and effort have been directed at preserving the improbable lean that has made the tower famous, earned it UNESCO protection and entices a million tourists to visit it each year. We find this amusing and quintessentially Italian: the Leaning Tower of Pisa is a beautiful but otherwise unremarkable bell tower, internationally famous because it was built with flawed and seriously under-engineered footings.

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