cities in the world. for now, that is. with 30 million tourists and almost 500 cruise ships passing through the lagoons each year, the citys literally falling apart. unesco is threatening to withdraw venice's world heritage status. now locals, many of whom earn their living from the travel industry, are calling for more sustainable tourism. reporter: every time tour guide paolo patuzzo crosses the rialto bridge, he can't help but wonder where did his charming city go? the one that's now overrun with millions of tourists? how can venice protect itself from the onslaught of visitors? he's sure this piece of world cultural heritage won't survive as a photo backdrop alone. paolo patuzzo: my love for this city makes me seek out places and people who are keeping venice alive. because there are enough people who are countersteering and navigating the city into troubled waters. reporter: like most venetians, paolo lives from tourism, which presents him with a dilemma. he now conducts special tours to draw attention to the city's problems, like in his own district, where rents are rising as flats are being used as holiday homes. m

city's agagile fodatitions. hthks to s unique canals,lagoon cityromantic alleyways, andists renaissance architecture, venice is consideredf the most beautiful cities in the world. for now, that is.