The Leaning Tower of Pisa was built to be a freestanding bell tower for the cathedral in Pisa's Piazza del Duomo. The bell tower was to be used to alert churchgoers in Pisa when it was time to attend services.
The Tower of Pisa was constructed in three stages over a period of almost 200 years. In 1173, construction began on the foundation and ground floor of the tower. A mere 10-foot foundation set in unstable soil caused the tower to begin sinking by the time the third floor was built in 1178. After a long interruption caused by external conflict, construction resumed in 1272, with engineers building subsequent floors with one side higher than the other to compensate for the tilt. A military defeat In 1284 forced a second interruption of the project. The seventh floor of the Tower of Pisa was completed in 1319, though the bell chamber was not built until 1372. The seven bells of the Tower of Pisa, one for each note in the musical scale, were added through 1655.
There is a lot of speculation over the identity of the original architect of the Tower of Piza. Some have speculated that Guglielmo, a 12th century Pisan artist, along with sculptor Bonanno Pisano, were the original architects. Others suggest that Diotisalvi, another 12th century Pisan architect, is responsible for the tower's design. In any case, Tommaso di Andrea Pisano, who built the Leaning Tower's bell chamber, was responsible for harmonizing the Gothic and Romanesque styles of the tower.
The Leaning Tower of Pisa underwent a period of structural strengthening from 1990 to 2001, with the angle of the tilt being decreased from 5.5 degrees to about 3.99 degrees. In 2008, Italian engineers announced that the tower had stopped moving for the first time in its history and estimated that because of the structural strengthening, the tower would be stable for the next 200 years. As of 2009, the Leaning Tower of Pisa is undergoing a gradual surface restoration to repair cracks and blackening due to the tower's age and exposure to the elements.
The Leaning Tower of Pisa has repeatedly played an important role in Italian as well as world history. Galileo Galilei is said to have used the tower to complete an experiment in gravity, according to notes written by Galileo's secretary. In World War II, the Leaning Tower was nearly destroyed by Allied soldiers who had received intelligence that the Nazis were using it as an observation post. A U.S. Army sergeant's decision not to call in an artillery strike saved the historic tower. In 1987, the Leaning Tower of Pisa, along with the Piazza del Duomo, was declared a UNESCO World Heritage Site, ensuring that the tower will be preserved for the enjoyment of generations to come.
