This week in 1990, the Leaning Tower of Pisa was closed for repairs. The problem: it was leaning too much.
Today, the tower is back where it belongs—not straight, because what kind of person goes to visit the Vertical Tower of Pisa?—but leaning about 18 inches less than before. The 1990 closure was the first time in the tower's long life that it was was closed for repair.
“Few monuments have been studied as much by engineers as the Leaning Tower of Pisa,” write scholars Ronald I. Borja, Giovanni Calabresi, James K. Mitchell and Robert L. Schiffman.
The fact that the Leaning Tower of Pisa has even made it this far is a fortunate historical accident. The tower was built over a period of 200 years, between 1173 and 1372 A.D.
“While some architectural follies are the product of unforeseeable bouts of bad luck, the Leaning Tower of Pisa’s signature tilt could have been avoided with better planning,” writes Michael Arbeiter for Mental Floss. “A shallow foundation and the soft ground of Pisa—composed of sand, clay and deposits from the Tuscan rivers Arno and Serchio—were too unstable to support the building even in the early stages of its construction.”
It was designed to be the third part of a cathedral complex, a white marble tower standing 185 feet high. To put its height in perspective, that’s one-third the height of the Washington monument, which, at 555 feet high, remains in 2017 the world’s tallest stone structure.
At that point, fortunately for the landmark, war broke out between the Italian city-state of Pisa, where the tower was being built, and Genoa. Almost 100 years passed before anyone worked on the tower again, writes History.com, a delay that likely allowed the foundation to settle enough to prevent it from falling over during construction.
Then in 1275 A.D., the next architects to take over the project added three additional floors that bent in the opposite direction of the tower’s northward lean, reports the Getty. Alas, the added weight had more impact than their intended fix, and the tower leaned even farther. The last part of the tower, the belfry where the bell was housed, was finished by yet another architect, between 1350 and 1372 A.D., the museum reports.
"It took some 200 years to complete the Tower, but there were only about 20 years of actual work. Talk about a nightmare construction project!" writes Alicia Ault for Smithsonian.com.
As a result of all this jostling, the tower now leans southward. Over the centuries, despite the efforts of many, it leaned farther and farther, leading to the closure. The tower didn’t reopen for 11 years, and even then, it was still slowly tilting. Even now, Ault writes, the tower is imperceptibly on the move.
But although the tower is ever-shifting, in its lifetime its quirky architecture has been hugely beneficial for Pisa and Italy. It's one of the nation's most distinctive tourist attractions, although you have to imagine that the combined weight of the millions of tourists who have climbed the tower must have had an impact on its lean.
If you visit Pisa today, you can climb its leaning tower and look out across Pisa as so many others have done over the centuries. The challenge might be choosing which leaning tower to climb: because of the region’s soft ground, several other church towers in Pisa also lean, Arbeiter writes, although none so dramatically.