The Leaning Tower of Pisa is one of the most famous structures in the world, not only for its dramatic tilt but also for its long and interrupted construction history. Unlike modern buildings that are completed in a few years, the Tower of Pisa took nearly two centuries to finish. Wars, political struggles, engineering mistakes, and financial challenges all shaped its timeline. Below is a detailed, step-by-step account of how the tower was built.
1. Planning and Foundation (1173)
Construction began in August 1173 in the Italian city of Pisa. At the time, Pisa was a powerful maritime republic. The tower was planned as a bell tower (campanile) for the Cathedral of Santa Maria Assunta in the Piazza dei Miracoli.
The original architect is believed to be Bonanno Pisano, possibly working with Guglielmo di Innsbruck. The foundation was laid on soft ground made of clay, sand, and silt. It was only about three meters deep, which later proved to be a serious design flaw.
2. First Building Phase (1173–1178)
During the first five years, workers completed the foundation and the first three floors. By 1178, the tower began to lean as the ground beneath one side sank. Construction was immediately stopped.
3. First Long Pause (1178–1272)
Work was halted for nearly 100 years due to the structural problem and wars with neighboring cities such as Genoa and Florence. This pause allowed the soil to settle and likely prevented collapse.
4. Second Phase (1272–1284)
Construction resumed under Giovanni di Simone. He tried to correct the lean by building the upper floors taller on the sinking side. Three more floors were added. The tower developed a slight curve.
Work stopped again in 1284 after Pisa’s naval defeat by Genoa.
5. Second Pause (1284–1360)
The tower remained unfinished for over 70 years.
6. Final Phase (1360–1372)
The final stage was completed by Tommaso di Andrea Pisano, who added the bell chamber at the top. The tower reached its final height of about 56 meters.
7. Later Repairs (19th–21st Century)
Numerous attempts were made to stabilize the tower. In 1990, it was closed, and after 11 years of engineering work, it was reopened in 2001.