Bologna Looks to the Leaning Tower of Pisa for Tips to Stop Garisenda’s Tilt

Leaning for centuries at a worrisome tilt, the Garisenda Tower in Bologna has endured insults and trauma. Dickens called it “sufficiently unsightly,” if extraordinary, while Goethe said it was “a spectacle that disgusts.” And then there were the earthquakes, the Allied bombing raids of the city during World War II and urbanization that doomed other towers.

The Garisenda has stood through it all, a beloved symbol of this medieval city, a reminder of a past when important families or communities would erect towers to remind others of their status, and for defense.

But now, the Garisenda is in trouble.

After sensors attached to the monument, which leans at a 3.6 degree angle, picked up “anomalous movements” last year, alarmed experts issued what one called an “engineering code red.”

In October, the Garisenda was cordoned off, with bright red protective barriers set up along part of its perimeter to limit the damage should the tower tumble, and a group of experts got to work on plans to safeguard it for the future, while watching for signs of imminent trouble.

“It’s like a patient in intensive care, there are 64 instruments that continually monitor its vital signs,” said Gilberto Dallavalle, a structural engineer responsible for the interventions to stabilize the 157-foot tower since 1997.

He and other experts called in to try to safeguard the tower have now put forward a solution, looking to another famous leaning tower for the answer. Bologna’s mayor, Matteo Lepore, announced last week that the city would adopt a temporary system of pylons and cables that proved a success in Pisa, where the most famous leaning tower is.

The idea is for two pylons to be attached to a special structure on the tower with cables that are expected to exert a counterforce should the tower start tipping more dangerously.

Once the Garisenda has been stabilized so that workers can operate safely, work can begin on shoring up the tower, especially the foundation, by injecting a mix of mortar compatible with selenite into a cavity in the base. A final phase will involve the restoration of the upper parts of the tower to ensure that it remains stable in years to come.

“We have to secure the situation as soon as possible so that it doesn’t get worse,” then more considered decisions can be taken, Mr. Lepore said of the initial phase of work.

Bologna may best be known for its rich food (one of its nicknames is “la grassa,” the fat one); its university, which is the oldest in Italy (another of its nicknames is “la dotta,” the learned); and its miles of porticos, which three years ago were listed as a UNESCO World Heritage Site.

But it was once also a multi-towered city, a medieval Manhattan (and yes, that made for yet another nickname, “la turrita,” the towered.)

The towers, which once numbered around 100, are now mostly gone, felled during the centuries or incorporated into palazzos and modern buildings. Among the 20-odd that remain, the Garisenda and its much taller neighbor, the Asinelli, have become the centerpieces of the city’s well-preserved medieval city center.

Prized symbols of the city, the towers are ubiquitous: on postcards, souvenir magnets, even on gigantic chocolate Easter eggs that featured a drawing of them on a marzipan surface.

Built in the 12th century by the Garisendi, a wealthy local family, the leaning tower began to tilt while it was under construction and was shortened by some 40 feet in the 14th century over fears that it could collapse. Over the centuries, it experienced considerable wear and tear, between exposure to the elements and two major fires. For at least 250 years, blacksmiths used a forge built inside the base of the tower that significantly deteriorated the fragile selenite stones at the base. The forge was in operation until the late 19th century.

Modern concerns about the tower’s stability began about 25 years ago, and it has been closely monitored since then.

Those efforts were intensified about five years ago, when it became apparent that “the pace of deterioration had picked up,” said Raffaela Bruni, the engineer who heads the committee of experts tasked with saving the tower. In 2021, the base was girdled by thick steel cables and wooden planks (picture oversized dental braces), and the dozens of sensors and other monitoring instruments that now pick up even minute shifts.

Currently, the protections put in place keep visitors about 65 feet away from the base of the tower.

The committee of experts decided on the pylon system after a recent fact-finding trip to Pisa, where they determined that the same system could be used with some modifications. If all goes well, the pylons should be ready in six months.

In Pisa, the work done on the tower has boosted its expected life span by another 300 years, said Massimo Majowiecki, a Bologna based engineer, who worked in Pisa and is now on the team in his hometown. The costs of maintaining Italy’s vast cultural patrimony, he noted, is “an enormous burden, but it also creates a lot of experience.”

There is no way of judging if the intervention in Bologna will work, or for how long, but the engineers hope that computer modeling will help. A team from the University of Bologna is developing a digital twin for the Garisenda to simulate the effects of any potential fixes.

For now, despite media reports questioning the tower’s stability, the local community seems mainly sanguine.

The Garisenda has “gone through a lot, and it’s never fallen,” said Maurizio Pizzirani, whose wife owns the Hotel Garisenda, a small inn overlooking the towers.

The hotel’s website now gets considerable traffic, he said, thanks to a 24-hour webcam outside a window of the hotel’s breakfast room that looks onto the towers, keeping tabs on the work. (Three towers were demolished decades ago to make way for the building the hotel partly occupies.)

Like other locals, Mr. Pizzirani had opinions about the best course of action to take (starting with rerouting large buses), though he acknowledged that the tower had “no instruction manual.”

Whatever the ultimate solution, the work on the tower is expected to be too expensive for the local government to handle alone.

A fund-raising campaign promoted by Bologna City Hall reminds people that the towers are part of the city’s history and says “now you can be part of it too.” So far, the campaign has raised 4 million euro, or $4.3 million, according to a city spokesman, which has covered the costs of the work done so far. Italy’s culture ministry has another 5 million euro for the restoration, and the regional government will also pitch in.

In coming weeks, rockfall nets are set to be raised at the base of the tower in front of the Asinelli tower and the adjacent baroque Basilica of Sts. Bartolomeo and Gaetano to limit damage in case of collapse.

The church is most at risk, but a recent visit inside showed no evidence that the priests had planned for the worst.

“Not having any specific know-how in the field, I’m going with what City Hall tells us,” said the Rev. Stefano Ottani, the parish priest of the basilica. “We haven’t been told to limit access or close the basilica, so we’re keeping it open.”

Ms. Bruni, the engineer, provided a different explanation: “They have great faith in the Lord,” she said with a smile.

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