Here’s How Engineers Have Managed To Straighten The Leaning Tower Of Pisa

For centuries, the Leaning Tower of Pisa has been looming over the Piazza dei Miracoli in Tuscany, Italy — its majestic figure beautifully askew. Once considered an architectural flop, the iconic Italian landmark is now a popular tourist attraction and has remained imperturbably askance.

The same tilt that has tipped the Tower of Pisa on the path to fame also threatened to bring its downfall. For this reason, the medieval monument was closed to the public in 1990 to undergo an extensive restoration work that ultimately kept it from toppling down.

The rescue efforts not only prevented the beloved monument from ending up a pile of rubble but also had long-term effects on the tower’s poise. As the Inquisitr recently reported, the Tower of Pisa has straightened over the 20 years, shaving off 1.5 inches from its emblematic tilt.

Why Is The Tower Of Pisa Leaning?

According to, the Tower of Pisa began to lean almost right from the get-go. The monument has been leaning for nearly 850 years, ever since the masons began its construction back in 1173.

The reason for this unexpected twist of events was put down to the soft ground on the tower’s south side, which caused the monument to lean in that particular direction.

“When they were building it, there were attempts to straighten it (by adding stone on one side), so it has a slight banana shape,” said engineer Roberto Cela, who is the technical director of the Opera della Primaziale Pisana — the organization set up to supervise the construction works of all the monuments in the Piazza dei Miracoli.

Since the tower’s slanting tendency would have eventually caused it to collapse, engineers undertook a laborious restoration project that helped reduce the monument’s gradient. The project lasted for eight years, spanning between 1993 and 2001.

How To Straighten A Leaning Tower

The Tower of Pisa measures a little over 183 feet on its low side and almost 186 feet on its high side. The monument has a base diameter of 50.5 feet and weighs 16,000 tons.

So, how did engineers manage to stop it from leaning any further and even got it to straighten up a bit? Cela explains the process in a nutshell.

“We installed a number of tubes underground, on the side that the tower leans away from. We removed soil by drilling very carefully. Thanks to this system, we recovered half a degree of lean.”

The arduous restoration work paid off and saw the Leaning Tower of Pisa straightening its posture by 17.5 inches in the last 25 years. The monument unbent its reclining figure by 16 inches by 2001, and by another 1.5 inches since then.

Although the tower has been officially re-opened to the public for 17 years, engineers are constantly monitoring its movements, taking precise measurements on an hourly basis. This has led to a better understanding of how the Leaning Tower of Pisa began to lean a little bit less over the years.

“The tower tends to deform and reduce its lean in the summer, when it’s hot, because the tower leans to the south. So, its southern side is warmed and the stone expands. And by expanding, the tower straightens,” said Nunziante Squeglia, a professor of engineering at the University of Pisa, who works with the Surveillance Group that monitors the tower’s restoration work.

The monument is reportedly continuing to straighten and it will keep doing so for many years to come, notes Cela. However, the engineer points out that there is no danger of it losing its quintessential charm: the Leaning Tower of Pisa “will never be completely straight.”