More than half of Venice was left under water when the historic lagoon town was hit by exceptionally high tides this week.
Water levels rose above 1.37 metres on Wednesday and remained above critical levels for 15 hours on Thursday, authorities said. It was the highest tide level since December 2010.
Venice starts flooding when waters rise 1.07 metres. When the 1.37 metre mark is reached, almost 60 per cent of the city is under water.
On Thursday, the famous St Mark's Square was 60cm under water. Tide levels were expected to return to more normal levels yesterday.
Chioggia, a town on the southern edge of the Venice lagoon, was the worst-hit area. Tides reached a peak of 1.62 metres, the third-highest level since 1966, when the area was devastated by a huge flood.
Venice, built on hundreds of small islands, often experiences high water in autumn and winter, causing floods to the city's narrow alleyways and squares, including St Mark's Square.
The authorities are building a dam system, the MOSE (modulo sperimentale elettromeccanico, or experimental electromechanical module), meant to insulate the city from tides above 1.07 metres.
But cost overruns, delays and opposition from green groups has hindered its construction. MOSE is now expected to cost more than US$7.8 billion and become fully operational in 2016.