Slowly, gradually, Venice is sinking. In the last century, the marshy land that the city sits on has lowered by about 11 inches.
But the far greater threat is the rate at which the sea level is rising. In recent years, Venice's acqua alta, or high water, has resulted in an average of 100 floods a year. The increasing sea level is largely a consequence of climate change.
Since the Great Flood of 1966, which displaced 5,000 people from their homes and destroyed $6 billion worth of treasured artwork, Italy has been working on a plan to fight back the waters of the Adriatic Sea. That plan has become Italy's biggest public works project ever.
The MOSE Project, or Experimental Electromechanical Module Project, is scheduled to begin operating next year. MOSE, named after Moses and the parting of the Red Sea, is a system of floodgates seeking to protect the Venetian Lagoon from becoming inundated with water from the sea. When inactive, the gates will lay flat on the seafloor; when water levels rise, they will be pumped full of air and rise above the surface to block sea water.
This project is so controversial, though, that it took almost four decades of political fighting for construction to start. Eight years and several billion dollars later, experts are still unsure about MOSE's ability to save Venice.
"Venice is in serious, serious trouble," said John Keahey, author of Venice Against the Sea: A City Besieged. "It's in danger from high water, and increasing frequency of high water, and it's in danger from out-of-control tourism."
This expert, who has a new book coming out this year called Seeking Sicily: A Cultural Journey through Myth and Reality, is one of many to express concerns about MOSE. He chatted with Travelwise this week and helped us break down the key concerns surrounding this sensitive project and Venice's unsteady future.
No plan but this plan
"[The government] never did the analysis to know whether another plan could have been more extensive or less extensive," said Keahey. In all the years of debate, the government failed to consider other viable proposals. Keahey points to such models as the Netherlands' Delta Works system, which includes not just floodgates but also sea walls standing as high as 40 feet above sea level.
Many environmentalists and scientists worry that floodgates could damage the lagoon's ecosystem and harm its wildlife -- especially since they would have to be lifted often, due to the high frequency of flooding.
Billions and billions of dollars
So far, MOSE has cost Italy more than $7 billion. Over the years, some politicians have argued that the acqua alta problem does not merit such an expensive solution since it has not resulted in any deaths. Others, Keahey included, warn of the dangers of waiting until people are killed and infrastructure destroyed before developing a solution. "My fervent hope is that there will be loud enough voices to continue searching for ways to keep the city from being under water."
A short-term solution to a long-term problem
Above all, Keahey fears that MOSE is a short-term solution to what could be a never-ending problem. He does not believe that the floodgates will remain effective for the 50 to 100 years that the government has talked about. "I believe the government is worried about other things," he said. "Like most politicians, [Italy's politicians] are only worried about the next election. They don't look 20 or 30 or 50 years down the road for future generations."
With all the time and money that has gone into MOSE, Keahey hopes the project will be a success. If the floodgates prove ineffective, though, Unesco and the European Union may eventually step in to help develop a long-term solution to help save this World Heritage Site.
"I love that city... I just hope there's a place for my grandkids and great-grandkids to go to," Keahey said.
Travelwise is a BBC Travel column that goes behind the travel stories to answer common questions, satisfy uncommon curiosities and uncover some of the mystery surrounding travel. If you have a burning travel question, contact Travelwise.