This Day in History: 1990-01-07

In 1990 the Leaning Tower of Pisa, Italy was closed to the public for the first time in history, due to fears of public safety.

The Leaning Tower of Pisa is the freestanding bell tower of the Cathedral of Pisa, Italy. Construction began in 1173 and continued over 199 years. The tower began tilting during its construction due to the soft, unstable ground beneath its foundation. Efforts to correct the tilt were made throughout its history, but the lean persisted and worsened over time.

By the late 20th century, the tilt had reached an alarming angle of 5.5 degrees, and experts warned that the structure was in imminent danger of collapse. In response, the Italian government and international experts decided to close the tower to the public and launch an ambitious preservation effort.

During its closure, a team of engineers, architects, and historians worked to stabilize the tower. Measures included:

• Adding counterweights to the base of the tower to reduce the tilt.
• Removing small amounts of soil from beneath the foundation on the northern side to gently correct the lean.
• Reinforcing the structure with cables and braces during the process.

After a decade of careful restoration, the tower was reopened to the public in 2001. The tilt was reduced to 4 degrees, the level it had in the early 19th century, and deemed stable for the foreseeable future.