August 9, 2023 – Leaning Tower of Pisa

850 years ago today, construction started on the Leaning Tower of Pisa! It took 199 years to complete, as the Republic of Pisa was constantly engaged in military conflicts with other Italian states. The tower began to sink after construction had begun on the second floor in 1178. This was due to it having a shallow foundation and the soil being very soft and unstable. Construction was stopped for nearly a century – which was actually a good thing, as it allowed the underlying soil to settle. Otherwise, the tower would have certainly toppled. When construction resumed, the architect and engineer tried to correct the leaning issue by making the rest of the stories shorter on the uphill side. But it kept leaning more and more, and by 1990 the tilt had reached 5.5 degrees.
Between 1993 and 2001, remedial work was done at the site to stabilize the soil, reducing the tilt to 3.97 degrees. In 2008, engineers announced that the Leaning Tower of Pisa had been stabilized and had stopped moving for the first time in its history. They said it should be stable for at least 200 years.
During World War II, the Allies suspected that the Germans were using the tower as an observation tower – which they were. Despite its tilt, the German army felt it was a good lookout point because they were able to see clearly over the surrounding flat terrain. But, when the advancing U.S. Army was told to demolish all enemy buildings and resources in 1944, the soldiers were so impressed by the beauty of the tower and the cathedral that they refrained from ordering an artillery strike, saving it from complete destruction.
Surprisingly, the Leaning Tower of Pisa isn’t the only building that’s leaning in Pisa. There are several other structures in the city that also have foundational instability, including 2 churches. It’s not the world’s most lopsided building – that honor goes to the Montreal Olympic Stadium Tower, which is 541 feet tall and has a curved angle of 45 degrees. Learn more here.