The worst flood in Venice occurred on November 4, 1966. The flood, known as the acqua alta or high water, was caused by a combination of factors, including high tides, a severe storm, and the city's sinking into the marshy Venetian lagoon.
The water level reached a peak of 194 cm (76 inches) above sea level, causing extensive damage to buildings, homes, and businesses. St. Mark's Square was flooded with over a meter of water, causing significant damage to the Basilica's interior and precious artwork.
The flood of 1966 was a wake-up call for Venice and the Italian government, leading to the development of a major program of measures to protect the city from future floods, including the construction of the MOSE project, a system of mobile flood barriers that can be raised to protect the city during high tides.