What caused the Leaning Tower of Pisa to lean?

The Leaning Tower of Pisa was completed in 1372. It has seven floors and is made of marble and stone. The tower was originally designed as a bell tower.

It began leaning during construction. Due to poor foundation, it could not support the weight of the tower.

By 1990, the tilt was 5.5 degrees. The fear was that the tower would continue to lean to a point of no return if something wasn’t done to control the leaning. It was stabilized between 1993-2001, which reduced the tilt to 3.97 degrees.

The Tower is a World UNESCO site, which attracts thousands of visitors each year.

More Info: en.m.wikipedia.org

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26 Comments

Terry Bremer

...If there were an Unstable Foundation, would it NOT be an Architectural Miscalculation NOT to have discovered that 'little' problem before construction began?

Chris Lee

We got to visit Pisa, and paid the extra 25 euro to get inside to take the circular stairway to the top. 20 year old guys were bounding up it like nobody's business, but this (2 years ago) 65 year old tuckered out by the second turn...the lean is so severe, it was that taxing. I;ve made it to th e top of a few lighthouses, and even St. Paul's in London, though. Maybe next time!

Irene Townsend

It has had an unstable foundation for centuries, I'm surprised it's still standing

David Coe

A few bits of rusty scaffolding would fix that !

kpkennedy

Unstable foundation is an Architectural Miscalculation. Geezer quiz club quit putting 2 correct answers to a question and making one of them incorrect.