The Leaning Tower of Pisa is a medieval bell tower that began construction in 1173, making it over 850 years old. It was built during the Middle Ages as part of Pisa’s cathedral complex, at a time when the city was a powerful medieval republic. The tower is traditionally credited to Bonanno Pisano, though several builders worked on it over centuries. The famous lean started almost immediately. The ground beneath the tower was made of soft clay and sand, causing one side to sink as the upper floo