Why does the tower lean? When the foundation was set, it was built on weak soil and sunk on one side. Due to financial constraints and battles going on, construction was halted for roughly 80 years. This allowed the foundation to settle in and become stable. At which point, it was decided they would finish construction and to compensate for the lean, they attempted to build one side taller than the other. A futile attempt, but you can see a slight curve in the building because of it. Since, they have reinforced the building and even reduced the lean to ensure it doesn’t topple over.
If ever you go to Pisa, just know that it is the only thing in town worth seeing. I took an afternoon and rode the train in from Florence and left.