Tourists have been warned to stay away from Venice which has been hit by the biggest flood in more than 20 years.
A combination of heavy rain and high winds has led to the sea levels in the romantic Adriatic lagoon city rising 5ft above normal.
It was the fourth-highest level recorded over the past century and there were fears that the water could rise further if more bad weather materialises as forecast.
Many of Venice's streets, including the famous St Mark's Square, one of the city's lowest points, were submerged, forcing people to wade through knee-high water.
Ferry and water taxi services were suspended and some luxury stores were also flooded.
Boxes of tourist merchandise floated inside the swamped shops around the square and even the city's famed pigeons sought refuge on rooftops and windowsills.
Alarms went off at 6.37am to alert citizens, but many residents were taken by surprise because authorities had initially not forecast such a high water level.
Mayor Massimo Cacciari warned those planning a visit to "think again" adding that those already in the city should stay indoors.
"It's an exceptional acqua alta,' and unless you absolutely have to, don't go out," he said.
The city would not ask for a state of disaster to be declared since the flooding did not cause any deaths or trigger the collapse of buildings, the mayor added.
But the official overseeing Venice's architectural heritage warned the city was reaching its limits and said the water was receding at a worryingly slow rate.
The Foreign Office urged tourists to check the FCO website for any updates.
Workers were unable to install the raised wooden walkways used during flooding because the water rose too quickly under heavy rains.
In St Mark's Square tourists tried to stay dry by hopping on cafe tables and chairs sticking out of the water. The water was so high that one rowed a small speedboat across the wide square.
