Venice may have stood for hundreds of years, but its population is recycled every few days as tourists come and go. For residents, such an influx is edging them out, reports the BBC's Christian Fraser from the Italian city.
Mattia Baseggio runs a guesthouse in Venice: Number 3749, Sestriere di Cannaregio.
The guesthouse at no 3749 has a splendid view
It is one of the great peculiarities of Venice: locals do not follow street names - they follow numbers and neighbourhoods.
The guesthouse oozes all the history and charm you would expect of a Venetian house.
It has been lovingly restored by Mattia's wife, an architect, and filled with the family antiques.
It has a splendid private garden in which the guests have their breakfast and it looks out over the Ponte Chiodo, the only remaining bridge of its kind in Venice.
It is a perfect place for a holiday.
But Mattia's bed-and-breakfast was once a private house. It has been converted from two empty family apartments that had been left to ruin.
Many of the families who lived in Venice for generations are moving out.
The tourist population of Venice changes every few days
House prices are impossibly high - empty apartments and buildings have been snapped up by wealthy hoteliers - and young people can no longer afford the cost of living.
"Almost half my friends have disappeared," said Mattia. "This is now one of the only ways to earn a living in Venice.
"The easiest thing to do here is to run a guesthouse. If you want a profession or a career you have to move away."
Over the past 50 years, thousands have taken part in this collective disappearing act.
The population of the historic centre of Venice has fallen from 171,000 residents in 1951 to fewer than 62,000.
Officials say the exodus shows no signs of abating - another 8,000 are predicted to follow in the next 10 years.
But as Venetians leave, the tourists continue to arrive. Eighteen million tourists come to Venice every year.
It is impossible to get onto a Vaporetto river-bus without finding it packed with suitcases and tourists.
"Some of them come looking for the real Venice," said Mattia. "But 80% of them come for a day, visit St Mark's and disappear. They miss the very essence of Venice. And it's a culture that is fast disappearing."
There is no hiding the changes around Venice. Shops are disappearing. Some neighbourhoods now have no grocery shops for local residents.
Souvenirs fill the old Ritz cinema. There used to be 10 cinemas in the centre of Venice, but now there is just one.
The city is swamped with high-priced designer shops, which might interest the day-tripper, but are of little use to people who live in the city.
"People have been leaving Venice since the 50s," says Venice Mayor Massimo Cacciari.
"It is nothing new. But the population is now so small it's critical we address the reasons why they are leaving.
Many of Venice's grocers are packing up and leaving
"We have to protect their way of life. We have to guarantee cheaper houses, we have to tackle the traffic problems on the canals, we have to improve public services.
"It can only be done if the state contributes and if it provides extraordinary finance to protect our buildings and our culture."
Today a 100-sq-m (1,000-sq-ft) apartment in Venice sells for up to 800,000 euros ($1m; £540,000).
The council is trying to build cheaper housing. They have set out three areas of the city for the development of houses which will be rented to middle-class families.
But it is a difficult balance.
Venice can no longer exist without its tourists as they are the main source of income.
And in a city that faces a constant battle against rising water levels, it is money that is desperately needed.
"We must have the tourists," said Mr Cacciari. "We want them to keep coming.
"But it is not enough. This is becoming a city solely for tourism. Venice is becoming a museum."