How does the Leaning Tower of Pisa defy gravity?

“Defend why the environment affects the “lean” in the Leaning Tower of Pisa.”

— submitted by a student in Maureen Petricca's sixth-grade classroom at Frederick Nerge Elementary School in Roselle.

An architectural wonder because of its persistence to defy gravity, the eight-story Leaning Tower of Pisa is part of a complex of church buildings called the Piazza del Duomo in the western Italian town of Pisa.

The complex is world-renowned for the striking Romanesque architectural design and the surprisingly crooked campanile or bell tower. This architectural blooper has been declared a World Heritage site and attracts one million tourists each year.

Pisa, which means “marshy land,” has two more leaning structures throughout the town that are also bell towers.

Tower construction began in 1173 just behind the massive grey-and-white striped cathedral. The tilt was noticed during the building process and now the tower leans about 13 feet away from being vertical.

“When they started to construct the building they realized it was shifting and took a 100-year break,” said architect Scott Hezner of the Hezner Corporation in Libertyville. “Then they started up again and adjusted the construction to compensate for the lean, building it higher on one side than the other and flattening it out.” As a result, the building is actually curved, and two steps were added to the building's south side to account for the imbalance.

Hezner speculates that the tons of earth removed to carve out the foundation for the cathedral were dumped on site and the tower was built over that loose soil. “There were no codes or regulations — it was enter at your own risk,” he explained. “Today when it happens there's restoration. We make buildings safe and solid for the future.”

Renovations over the years bolstered the soft soil and stabilized the foundation, but the building still leans a little more than a millimeter each year. Without further intervention, it's likely the tower will tumble to the ground. Despite its lean, visitors can ascend the 296 steps to the tower's top.

You don't have to travel as far as Italy to see a half-scale replica of the Leaning Tower of Pisa — just to Niles, Ill.

Robert Ilg, owner of the Hot Air Electric Ventilating Company, built an employee recreation center in 1934 that included the Leaning Tower replica, swimming pools and a toboggan run.

The charming tower covered a water storage area that held tanks for swimming pools. His family donated the complex to the YMCA in 1960 and it has since been known as the Leaning Tower “Y.”

A bronze plaque on site compares the original Leaning Tower of Pisa's dimensions to this mini-me model.