The history of the Leaning Tower of Pisa began on August 9, 1173, when construction started on the freestanding bell tower (campanile) for Pisa's cathedral. The tower's famous lean was never intentional; it started to tilt just five years into the project due to a shallow three-metre foundation laid in soft, unstable subsoil. This foundational flaw would define its 850-year history.
The Three Phases of Construction (1173-1372)
The tower's construction spanned nearly two centuries, a period marked by long interruptions that ultimately saved the structure from collapse. The work is divided into three distinct phases.
Phase 1: The Lean Begins (1173-1178)
Work on the white marble tower began during a period of prosperity for the Republic of Pisa. The original architect remains a mystery, though Bonanno Pisano is often credited. By 1178, as builders finished the third of the planned eight storeys, the tower had already begun to sink on its south side, causing a noticeable tilt. Shortly after, construction was halted for almost a century, largely due to ongoing military conflicts with other city-states like Genoa and Florence. This long pause allowed the soil to compact and settle, a crucial factor that likely prevented an early collapse.
Phase 2: A Curved Correction (1272-1278)
Construction resumed in 1272 under the architect Giovanni di Simone. In an attempt to counteract the lean, he engineered the new floors to be taller on the sinking side. This intervention didn't stop the lean but instead gave the tower its distinctive gentle curve. However, the added weight of the new storeys only exacerbated the problem, and work was stopped again in 1278 after the Pisans were defeated in the Battle of Meloria.
Phase 3: Completion of the Tower (1319-1372)
The seventh floor was finally finished in 1319. The bell chamber, the final level, was added by Tommaso di Andrea Pisano and completed around 1372. He managed to blend the Gothic style of the belfry with the Romanesque style of the main tower. Seven bells were eventually installed, one for each note of the major scale.
A History of Falling and Rescue
For the next 600 years, the tower's lean steadily worsened. By the 20th century, the situation had become critical.
"By 1990, the tilt had reached 5.5 degrees, the most extreme it had ever been, and engineers feared a collapse was imminent."
Modern Intervention (1990-2001)
The Italian government launched a major stabilisation effort, closing the tower to the public on January 7, 1990. An international team of engineers, led by John Burland, worked for over a decade to save it. The solution was a complex process of soil extraction. By carefully removing 38 cubic metres of soil from underneath the tower's raised north side, they managed to gently coax the structure back to a safer angle. The bells were temporarily removed to relieve weight, and the tower was braced with steel cables.
The Tower Today
The project was a resounding success. The tower reopened to the public on December 15, 2001, with its lean reduced to 3.97 degrees—similar to its position in the late 18th century. The structure is now continuously monitored and has been declared stable for at least the next 200 years. Its unintended flaw has made it a UNESCO World Heritage Site and one of the most recognisable landmarks in the world. To experience this incredible history, you can book guided tours of the entire Square of Miracles.
Frequently asked questions
Who built the Leaning Tower of Pisa?
The original architect's identity is not definitively known. While Bonanno Pisano is often credited with starting the project in 1173, other architects like Gherardo di Gherardo and Giovanni di Simone oversaw later stages of construction.
Why was the Tower of Pisa built?
The Tower of Pisa was built as the campanile, or freestanding bell tower, for the adjacent Pisa Cathedral. It is part of the larger religious complex in the Piazza dei Miracoli (Square of Miracles), which also includes the Baptistery and the Camposanto Monumentale (cemetery).
Has the tower always been leaning?
Almost. The lean began in 1178, only five years after construction began, once the structure reached its third storey. The unstable ground could not support the weight, causing the foundation to sink unevenly from the very beginning.
Walk through centuries of history by climbing the very steps that have tilted for over 800 years. Be sure to book tickets online to secure your place in this remarkable story.