The Leaning Tower of Pisa in Tuscany, Italy, was successfully stabilized and straightened by 44 centimeters following a delicate engineering operation that extracted soil from beneath its northern foundation.
Hungarian publication Startlap reported that decades of concern over a potential collapse were resolved through an international stabilization effort led by geotechnical engineer Michele Jamiolkowski.
The famous medieval bell tower had reached a critical structural threshold, prompting authorities to close it to visitors in January 1990 after more than 31 million tourists had climbed its steps during the preceding 60 years.
Rising Collapse Risks in Pisa
By 1990, the monument leaned at an angle of approximately 5.5 degrees. Computer modeling indicated that the threshold for structural collapse was around 5.44 degrees, leaving the tower separated from disaster by only hundredths of a degree.
Ground movements compounded the danger, pushing the top of the tower outward by roughly one millimeter each year.
The root of the instability dates back to August 1173, when construction began on soft clay soil that was incapable of supporting the nearly 14,500-ton structure evenly.
Medieval builders noticed the tilt during construction and tried to correct the angle by adding extra masonry on one side. This modification left the bell tower slightly curved as well as leaning.
Initial Cable and Lead Interventions
Early rescue operations in the modern era attempted to secure the landmark using heavy steel cables and structural steel bands.
Engineers also placed massive lead counterweights totaling around 870 tons on the higher, northern side of the foundation.
While these emergency measures slowed the movement, they were unable to significantly reverse the inclination of the building.
Soil Extraction Method and Engineering Stats
An international team led by Michele Jamiolkowski subsequently adopted a far more subtle approach known as soil undercutting.
Specialists drilled slanted boreholes beneath the northern foundation to remove small quantities of earth in a controlled manner.
The surrounding soil slowly compressed into the small cavities created by the drilling. This caused the northern side of the site to sink by several millimeters, pulling the top of the tower gradually in the opposite direction.
Major excavation work took place between 1998 and 2000 under continuous sensor monitoring.
Engineers removed a total of about 70 tons of soil, a volume smaller than the cargo capacity of two fully loaded semi-trailer trucks.
By comparison, the 14,500-ton tower weighs roughly twice as much as the metal structure of the Eiffel Tower in Paris, which weighs approximately 7,300 tons.
The undercutting process successfully altered the inclination of the monument, shifting the top of the bell tower back by 44 centimeters.
Reasons for Avoiding Concrete Fill
Engineers deliberately avoided pouring concrete into the foundations or using mechanical force to pull the tower straight.
Experts concluded that sudden or heavy interventions could endanger an eight-century-old monument resting on soft clay soil.
By working alongside natural soil movement, specialists avoided permanently adding large quantities of modern construction materials into the historic monument.
The soft clay soil that originally caused the leaning also provided an unexpected benefit, helping to absorb ground vibrations caused by earthquakes.
Reopening Costs and Ongoing Self-Correction
The total cost of the engineering rescue project reached nearly 28 million euros, which equals approximately 1.3 billion Ukrainian hryvnias.
Authorities reopened the Leaning Tower of Pisa to the public on December 15, 2001, following an eleven-year closure.
Upon reopening, the angle of inclination was reduced to roughly 3.97 degrees, returning the tower to a state similar to its alignment in the early 19th century.
Monitoring data showed that the monument continued to straighten on its own after human intervention ended, moving an additional 4.5 centimeters between 2001 and the late 2010s.
Engineers now consider the building stable for at least 200 years. However, the tower will never become entirely vertical, both because of soil characteristics and because the masonry itself was built with a slight curve.
Visitor Regulations and Ticket Prices for 2026
Visitors to Pisa can view the bell tower from the grounds of the Square of Miracles or purchase timed tickets to climb to the top.
In 2026, a standard admission ticket to the tower costs 20 euros, which is around 1,000 hryvnias, with no concession or discount tickets available.
A combined ticket for the full site costs 27 euros, or roughly 1,350 hryvnias, providing access to the tower along with all open museums and monuments on the Square of Miracles.
The climb consists of 251 steps and takes approximately 30 minutes. Official guidance notes that the stairs are uneven and slippery in places, making the ascent unsuitable for visitors with cardiovascular or musculoskeletal conditions.
Children who will not turn eight years old by the end of the current calendar year are not permitted inside the tower. Visitors under 18 years of age must be accompanied by an adult, and staff may request proof of age.
Entry Rules and Bag Restrictions
Ticket holders are advised to arrive at least 15 minutes before their scheduled entrance time. Late arrivals will be turned away without a refund.
Bags are prohibited on the climb, requiring visitors to leave handbags, backpacks, and luggage in a free cloakroom before entering.
Large suitcases are banned from the entire Square of Miracles complex, and small permitted bags must not exceed 20 by 30 by 38 centimeters.
Visitors may present official electronic tickets on a mobile phone, provided the barcode scans clearly.
Ukrainian news agency UNIAN previously reported that travel guide publisher Lonely Planet listed eight key destinations in Italy as top places to visit.
