The World Heritage site, built on an island in the centre of a lagoon in North East Italy, is visited by millions of tourists every year eager to float down the Grand Canal in a gondolier.
The famous city is already in danger of sinking into the sea because of subsidence and rising sea levels.
However the latest threat to Venice is more about economics.
Italian authorities want to build a major shipping port on the inland side of the lagoon that will allow more cruise ships and massive containers to go past the low lying island.
In a report put to the Italian government, the Venice Port Authority called for a new terminal at Marghera Port to deal with the increase in tourism and trade to the area. The authority also want to spend millions deepening shipping lanes in the lagoon.
Conservationists say it could be a “ecological catastrophe” for Venice as the continual dredging of the lagoon causes sea levels to rise.
In a report launched at the Royal Institute of British Architects, the charity Venice in Peril said waves generated by large ships and the currents that run through the deep passageways play a big part in dragging out the sandbanks that keep seawater out.
The report, written in collaboration with Cambridge University Department of Architecture, said buildings are already being destroyed as seawater gets into the brick work and then damages the infrastructure as the water dries out leaving salt behind. If levels continue to rise many famous buildings like St Mark’s Square could crumble altogether.
Nicky Baly of Venice in Peril said rising sea levels are already causing problems for most of the famous buildings in the city.
“The degradation of the lagoon adds to the long term rising sea levels eating into the brickwork of the buildings. Ultimately they will crumble because the structures will be unable to stand,” she said.
Venice is one of the busiest tourist sites in the world with more than 16 million visitors every year. In 2005 510 cruise ships up to 16 decks high came into the city, compared to just 200 in 2000.
At the same time the petrochemical industry in the area is dying and the Italian government is eager to promote tourism and trade with emerging markets in the Balkans and Eastern Europe.
The Venice Port Authority insisted it was necessary to improve Marghera Port to deal with the increasing flow of tourists and goods.
The authority said city will be safe because of a new £3.7 billion tidal barrier system known as MOSE, expected to be operational by 2014, that will stop flooding.
But Tom Spencer, Director of the Cambridge University Coastal Research Department, said the barrier will only stop tidal floods and do little to prevent sea level rise because of continual dredging.
“It is difficult to see how the implementation of the MOSE system legitimises the deepening of the navigation channels in the Venice lagoon at the present time. MOSE is an extreme flood control system but the problems in the lagoon are related to the long term evolutionary tendency,” he said.