They are relatively independent but form a unified Roman architectural style

The Leaning Tower of Pisa (Torre pendente di PisaTorre di Pisa), located behind the Cathedral of Pisa in the Miracle Square in the north of Pisa, Tuscany, Italy. It was built in August 1173 and is the independent bell tower of the Cathedral of Pisa. The exterior of the Leaning Tower of Pisa is made of milky white marble, which is relatively independent but forms a unified Roman architectural style. The Leaning Tower of Pisa is 58.36 meters high from the foundation to the top of the tower, 55 meters high from the ground to the top of the tower, the width of the bell tower wall on the ground is 4.09 meters, the width at the top of the tower is 2.48 meters, the total weight is about 14453 tons, and the center of gravity is 22.6 meters above the foundation. The circular foundation area is 285 square meters, and the average pressure on the ground is 497 kPa. The tilt angle is 3.99 degrees, deviating from the outer edge of the foundation by 2.5 meters, and the top layer protrudes 4.5 meters. The tilt was first discovered in 1174.