Tower of Pisa or The leaning Tower of Pisa is the bell tower of the Pisa’s cathedral, in Italy. What makes this tower so popular is his leaning which is something very unusual for a building. We expect a building to stand perpendicular to the ground.
The building has 56.7 meters on its high side and 55,86 meters on the low side.
The tower leans at about 3.99 degrees but before some restoration work the angle was 5.5 degrees. With this leaning, the top of the tower is displaced horizontally 3.9 meters from where it would be without it.
The construction of the Pisa Tower started in 1173 and it last for 177 (the building was constructed in three steps). It began with blind arcade as a ground flour. Five years later, when the second floor was started, the tower begin to sink because of an unstable subsoil. The construction was paused for almost one century because of the subsoil problem firstly but also because of the battles which involved Pisa. During this pause, the subsoil was consolidated to sustain the entire building. In 1198, the clocks were added to floor number three, despite the building was unfinished.
Almost one century later, in 1272, the construction resumed with next floors. The constructors tried to annihilate the leaning by constructing next floors with one side taller than other (that’s why in the beginning of the article we’ve talked about two different sizes).
The construction was halted again when Pisa was conquered (1284), but 35 years later the seventh floor was finally finished. Seven bells were added after that (last one three hundred years after the construction of the building was ended) – one fore each musical note.
Now, The Leaning Tower of Pisa is one of the most attractive point for tourists in Italy. It’s a common thing that most of them try to “hold it op” in pictures using “forced perspective” – an optical illusion. They stay in front of the camera with their hands or foots like they would stop the tower from toppling.
In WW2, the Tower an observation point for Germans. The Allied found that and they were close to order an artillery bombardment. But because of its history and cultural value, they aborted the plan.
Over the history, many mathematicians and engineers tried to find solutions for preventing the tower to fall. Last major intervention was at the end of the 20 century when the leaning angle was reduced with 1.6 degrees.