14 Intriguing Insights About the Leaning Tower of Pisa

While the Leaning Tower of Pisa is renowned as the ultimate backdrop for playful tourist photos (drawing 5 million visitors each year), this historic landmark offers far more than just amusing snapshots of loved ones pretending to support its tilt. Dive into the fascinating story behind Italy’s most famous architectural mishap.

1. Building the Tower of Pisa spanned two centuries.

Work on the campanile, or bell tower, adjacent to Pisa’s public cathedral began in August 1173. By 1178, the structure had reached its third level, already showing a slight northward lean. Conflicts with neighboring Italian states soon interrupted construction, which didn’t resume until 1272. Progress lasted only 12 years before another war brought work to a halt. The final phase of construction began in the early 1300s, culminating in the addition of the bell chamber in 1372.

2. The tower's lean is a result of poorly planned construction. 

While some architectural mistakes arise from unpredictable bad luck, the Leaning Tower of Pisa’s famous tilt could have been prevented with more careful planning. The combination of a shallow foundation and Pisa’s unstable soil—composed of sand, clay, and sediments from the Arno and Serchio rivers—was too weak to support the structure even during its early construction phases. Interestingly, builders identified this issue early in the two-century project: After the third story was added, the ground began to shift, causing the now-iconic slant. 

3. The tower’s lean once changed direction.

When construction restarted in 1272, the new additions worsened the tower’s stability. Adding more stories above the existing three shifted the building’s center of gravity, reversing the direction of its tilt. As the fourth, fifth, sixth, and seventh stories were built, the tower, which once leaned northward, started tilting increasingly toward the south. 

4. The story of Galileo dropping a cannonball from the Leaning Tower of Pisa may be a myth.

One of Renaissance physicist Galileo Galilei’s most celebrated discoveries was that gravity affects all objects equally, regardless of their mass. Legend has it that Galileo conducted an experiment in 1589 by dropping a cannonball and a musket ball from the Leaning Tower of Pisa. However, the only account of this experiment comes from his disciple Vincenzo Viviani’s biography, leaving its authenticity in question.

Contemporary scholars such as Paolo Palmieri and James Robert Brown suggest that Galileo’s Leaning Tower of Pisa experiment was likely a theoretical concept—possibly conceived later in his life—and never actually performed. They argue that Viviani exaggerated the story to enhance the significance of Galileo’s findings. 

5. Mussolini attempted to correct the tower’s lean but ended up exacerbating it.

In 1934, Italian dictator Benito Mussolini deemed the leaning structure a blemish on Italy’s image and ordered efforts to straighten it. Workers drilled hundreds of holes into the foundation and injected large amounts of grout, but this ill-advised approach caused the tower to sink further into the ground, increasing its tilt. 

6. During World War II, the tower served as a military observation post.

Despite its prominent appearance making it an obvious target, the German military utilized the tower as a strategic lookout during World War II, as its height offered an excellent vantage point over the flat surrounding landscape. 

7. American soldiers chose to spare the tower from destruction.

The German military’s use of the tower almost achieved what gravity could not—its collapse. In 1944, when U.S. troops were tasked with destroying enemy structures and resources, they were so captivated by the tower’s beauty that they refrained from targeting it. As veteran Leon Weckstein recounted in a 2000 interview with The Guardian, American soldiers advancing through Axis-occupied Pisa were mesmerized by the Leaning Tower and decided against calling in artillery. Weckstein described preparing to attack a Nazi base but retreating under enemy fire, leaving the iconic tower unharmed. 

8. The tower’s tilt continued to worsen over time.

Over time, the ground beneath the tower continued to weaken under its weight. What began as a slight 0.2-degree tilt grew steadily over the centuries, reaching a peak of 5.5 degrees by 1990—equivalent to the top being 15 feet off-center from the base. In the following decade, engineers stabilized the soil and installed anchors to address the tower’s dangerously severe lean. While these measures improved its stability, the tower continued to tilt. By 2008, a second stabilization effort successfully stopped the leaning for the first time. A 2022 study showed that, since 2001, the tower had self-corrected by an additional 1.6 degrees, with the first signs of self-correction observed in 2018.

9. The engineer who led the stabilization project wasn’t initially a specialist in the field.

On paper, John Burland seemed an unlikely choice for a project like stabilizing the Leaning Tower of Pisa. Burland confessed that soil mechanics, the engineering discipline crucial to the tower’s stabilization, was his weakest subject during his studies at the University of the Witwatersrand in Johannesburg. Despite this, he went on to become a professor at Imperial College London and played a key role in saving the Leaning Tower of Pisa from collapse. 

10. The tower’s tilt could still return in the future.

Without further interventions to prevent future tilting, the tower is expected to remain stable for the next two centuries. However, if conditions remain unchanged, the ground is likely to shift again in the early 23rd century, causing the tilt to gradually return. 

11. The Leaning Tower of Pisa isn’t the only leaning structure in Pisa.

Several other buildings in Pisa face foundational instability due to the city’s soft soil. These include San Nicola, a 12th-century church located about half a mile south of the Leaning Tower, and San Michele degli Scalzi, an 11th-century church roughly two miles east of the two. While San Nicola has a slight lean due to its buried foundation, San Michele degli Scalzi tilts significantly at 5 degrees. 

12. Other towers have rivaled the Leaning Tower of Pisa’s famous tilt.

While the Leaning Tower of Pisa is the most renowned for its tilt, other structures have rivaled its iconic slant. In 2009, the Leaning Tower of Surhuusen, a German steeple built between the 14th and 15th centuries, officially surpassed Pisa’s lean—Guinness World Records confirmed its tilt was 1.2 degrees greater than Pisa’s, which had been reduced from its peak of 5.5 degrees to 3.97 degrees. Other competitors include the 14th-century Oberkirche in Bad Frankenhausen, Germany, and the shorter of the Two Towers of Bologna, with leans of 4.8 degrees and 4 degrees, respectively. 

13. A rock formation in Antarctica is named after the tower.

Discovered by the French Antarctic Expedition, a massive rock dome in Antarctica’s Geologie Archipelago bears the nickname “Tour de Pise” due to its resemblance to the Leaning Tower of Pisa. This 27-meter-long formation, first recorded on Rostand Island in 1951, honors Italy’s iconic structure.

14. The tower’s soil may shield it from earthquakes.

Despite experiencing four major earthquakes since its construction, the Leaning Tower of Pisa has endured them all—a surprising feat given its tilt and unstable foundation. However, the soft soil may be its saving grace: According to the International Information Center for Geotechnical Engineers, researchers believe the tower’s stiffness combined with the soft ground mitigates seismic vibrations, preventing resonance and reducing the forces acting on the structure.