Why does the Leaning Tower of Pisa in Italy lean? It leans because of a mistake. It has leaned almost since the day the tower was built. In 1173, the people of Pisa, Italy, wanted to build a bell tower. They wanted the tower to be the most beautiful bell tower in all of Italy. The city also needed a bell tower because the church did not have one. However, there was a problem. As soon as the first floor of the building was finished, the tower started to lean. Builders tried to make the building straight again as they added more floors, but they couldn't figure out how to make it stop leaning. It took almost 180 years to finish the tower. Since then, the tower has leaned by another millimeter every year. Today, the Leaning Tower has eight floors and is 54.5 meters tall. By 1990, it was leaning by about 4 meters to one side. It was also slowly sinking into the ground. Many people became worried that it would soon fall apart. In 1998, repair works began on the tower, and by the end of 2001, it had been moved back by 45 centimeters. The tower will still lean, however, so it will need to be repaired again---in another 200 years. When did the tower begin to lean?
from the first day it was built after the first floor was built after the last floor was built 180 years after it was built