Construction began on Italy’s Leaning Tower of Pisa in 1173.
The tower was planned as the freestanding bell tower, or campanile, for Pisa Cathedral. Its foundation was laid in the Piazza del Duomo, alongside the cathedral and baptistery. The structure began leaning during construction because it was built on soft, unstable ground with a shallow foundation.
Work did not proceed continuously. Conflicts and wars interrupted construction, allowing the ground to settle between building phases. The tower was completed in the 14th century, nearly two centuries after its foundation was started. Its famous tilt therefore developed gradually rather than appearing as a completed design feature.
The tower is often wrongly attributed solely to one architect because the authorship of its original design remains debated. Stabilization work in the late 20th and early 21st centuries reduced the tilt while preserving the landmark’s historic appearance.