Why Does The Leaning Tower Of Pisa Lean?

This may be one of the most interesting questions simply because the tower was not meant to lean when it was designed and built. Yet, the fact that it does lean makes the tower one of the world’s most visited and photographed tourist destinations.

The Leaning Tower of Pisa is a bell tower associated with the cathedral in Pisa, an Italian city. According to historical records, the tower began to lean not long after it was built in 1173. The men who looked into the problem soon found that the foundation was not constructed properly. But that may be just one of the reasons the bell tower originally leaned to the southeast. The soil under the tower is loose and was not correctly compacted before the construction began. This also caused the tower’s foundation to move and it now leans in a slightly different direction (generally southwest).

Weight may have something to do with the tower leaning from the upright position. The structure is more than 180 feet tall and weighs thousands of tons. The tower walls would seem to be wide enough and sturdy enough to support that weight if it weren’t for the foundation and soil problems. The walls are 13 feet wide at the base.

Studies of the problem show that the tower leaned more than 5 degrees from vertical before workers tried to straighten the structure. Restoration work and foundation work put the tower at about 4 degrees from vertical. Construction of the tower was started nearly two centuries before it was completed. The design was intended to make the tower a work of art.

The original two levels of the tower didn’t lean but the structure began to lean when construction moved to the third level and beyond. Apparently the foundation was not sufficiently thick or deep. The soil at the chosen site was much too unstable to support such a large structure. In fact, work stopped completely for nearly a hundred years, not only because of the construction problems but because the country was a scene of constant battles between city-states.

Studies have shown that this work stoppage may have allowed the soil to settle enough to keep the tower from collapsing. Work started again in 1272. Construction workers tried to make up for the leaning by making one side of the tower taller than the other. But the Leaning Tower of Pisa started to lean in the direction of the taller side!

Work on the tower stopped again for a few years. In the 20th century, engineers and construction crews performed work to strengthen the tower and restore the surface of the structure. The government of Italy even financed an unusual attempt at keeping the tower from falling – lead weights on the side opposite the lean. In the long run, the decision was made to maintain the tilt since the tower was such a popular tourist destination.

The site was closed to the public for a time and soil was removed from the side opposite the lean to partially straighten the structure. Some bells and other objects were removed to reduce weight as well.

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