The Iconic Garisenda Tower of Bologna Has Leaned Too Much!

A leaning tower in Italy is at it again, and no, it’s not in Pisa! Rather, it is the Garisenda Tower in Bologna, and officials have now closed it off, along with the central square adjacent to it, fearing its collapse. A few meters apart from the much taller (double in height) Asinelli Tower, these ‘twin towers’ are historical symbols of the city, with the Garisenda remaining tilted 4 degrees for centuries. Recent surveys, however, have found ‘traces of unexpected rotation’ in the incline that have prompted immediate closure for ‘a number of years’.

The 48-meter (157.4 ft), 12th century medieval structure has prompted the Italian city’s mayor, Matteo Lepore, to call in the closure of Piazza di Porta Ravegnana, necessary in order to “save” the Garisenda Tower. “We’re not intervening because we think it could collapse at any moment, we’re intervening because we want to make it safe and restore it,” he said.

Unusual Sway: Appointing an Expert Committee

This discussion was prompted by the discovery made by scientists from the University of Bologna, who detected an unusual increase in the tower's swaying. The Garisenda tower, which had captivated the likes of Charles Dickens during his visit to Bologna, possesses a slant of 4 degrees, just slightly steeper than the more renowned Leaning Tower of Pisa in Italy, which tilts at 3.9 degrees, reports The Guardian. It is believed that the tower's slant can be attributed to ground subsidence that occurred during the 14th century.

The leaning tower of Pisa (CC BY-SA 3.0) and the two towers of Bologna: the Garisenda tower and the Asinelli tower far right. (Patrick Clenet/CC BY-SA 3.0)

Efforts are underway to monitor the tower for any signs of cracks, with the installation of sensors to track any potential movement. To enhance the tower's stability, its foundations will be reinforced with new materials. As a precautionary measure, the Asinelli tower, a popular attraction for visitors who climb it, has been temporarily closed for safety.

“Everybody agrees that the base needs to be reinforced, because of its historical weakness and because of the recent concerns raised by the data collected,” said Cleto Carlini, who is in charge of public works, green spaces and mobility at Bologna’s City Hall. “The question is how, and we need to study that thoroughly before planning the restoration,” he explained.

For numerous years, a dedicated committee of national experts comprising geologists, engineers, architects, and chemists has been analyzing the data gathered from the Garisenda Tower, collected through acoustic sensors, optical fibers, a GPS unit atop the tower, a pendulum, and groundwater monitoring systems near the tower's subterranean aquifer.

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Skyline of Bologna, including the Garisenda Tower and Asinelli Tower. (ecstk22/Adobe Stock)

Reinforcing the Garisenda Tower: A History of Swaying Restoration Plans

In the year 2021, the tower's base underwent the installation of substantial iron rings, encircling it to safeguard against potential cracks in its delicate selenite stone. As a preventive measure, iron rings were already introduced to reinforce the upper section of the tower, constructed from the distinctive red bricks typical of Bologna, dating back to the late 1990s, reports The New York Times.

The subsidence of the ground and the tower's foundations originated from the early 1100s, likely due to a construction error. By the mid-1300s, concerns about the tower's stability led to its partial shortening. The tower's noticeable forward-leaning posture even evoked fear in the renowned poet Dante Alighieri, who likened it to the appearance of the colossal figure Antaeus in his "Inferno," the inaugural volume of his "Divine Comedy”!

The towers bear the names of the influential families who constructed them. The two leaning structures stand as the iconic symbols of Bologna. (Guido/Adobe Stock)

In previous years, experts had proposed a solution involving the construction of a series of tall piers equipped with sturdy steel cables to support the Garisenda Tower and prevent any further deterioration of its leaning angle. However, this project was ultimately abandoned due to concerns that the extensive excavation required for the deep foundations of these piers might jeopardize the stability of the nearby Asinelli Tower.

Subsequently, a later restoration plan was conceived, involving the injection of a specialized type of cement into the base of the tower to fill the gaps that had formed in the selenite stone over time. However, this plan did not progress as experts determined that further testing was necessary before executing the project.

As the area surrounding the tower has now been restricted, the current plan entails the construction of bulkheads around the base of the tower to stabilize it. In the future, the 157-foot (48-m) tall tower will be enveloped in a protective enclosure as a restoration strategy is carefully selected.

Mr. Lepore acknowledged that it remains uncertain whether the experts will attempt to straighten the tower, fortify its base, or even consider partial disassembly and reconstruction to ensure a more robust structure. He assured that a safety net for the tower will be erected within six months.

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In 2021, the city of Bologna celebrated a significant achievement, as its extensive network of porticoes (extended colonades), running throughout the city, and totaling approximately 39 miles (62 km), was designated as a UNESCO World Heritage site. The city is now aspiring to expand this protected area to encompass both the Garisenda Tower and the Asinelli Tower.

“Having the two towers on the UNESCO list would help us in terms of promotion and visibility,” Mr. Lepore said, “but also in terms of maintenance and preservation for the future.”

Top image: The Garisenda Tower and Asinelli Tower in Bologna, Italy. Source: Aliaksei/Adobe Stock

By Sahir Pandey