The Leaning Tower of Pisa
After a photograph by Fratelli Alinari, published 1925?

The Leaning Tower of Pisa, originally intended to be a freestanding bell tower for Pisa's cathedral complex, began construction in 1173 under the oversight of architect Bonanno Pisano. However, due to the tower's foundation being laid in soft ground consisting of clay, sand, and shells, the tilt became apparent even during the initial phases of construction. As construction progressed, attempts were made to compensate for the lean, resulting in the tower's distinctive curved shape. Standing at approximately 56 metres tall, with its top reaching almost 3.9 metres off the perpendicular, the tower's tilt continued to increase over the centuries. Despite its lean causing concerns about its stability, restoration efforts were undertaken in the late 20th century, including the removal of soil from beneath the raised end and the installation of counterweights to mitigate further leaning. Today, the Leaning Tower of Pisa remains one of Italy's most visited landmarks, drawing millions of tourists annually to marvel at its architectural anomaly and rich historical significance within the Campo dei Miracoli, a UNESCO World Heritage Site. It considered one of the Seven Mediaeval Wonders of the World, a designation highlighting remarkable architectural and engineering achievements from the mediaeval period.