Venice is a preposterous monument to both the folly and the obstinacy of humankind. It shouldn't exist, but it does, much to the delight of thousands of visitors, gondoliers, lace makers, hoteliers, restaurateurs, and glass blowers.Centuries ago, in an effort to flee barbarians, Venetians left dry-dock and drifted out to a flotilla of "uninhabitable" islands in the lagoon. Survival was difficult enough, but no Venetian has ever settled for mere survival. The remote ancestors of the present inhabitants created the world's most beautiful city. To your children's children, however, Venice might be nothing more than a legend. The city is sinking at an alarming rate of about 2 1/2 inches per decade, and at the same time, the damp climate, mold, and pollution here are contributing to the city's decay. Estimates are that, if no action is taken soon, one-third of the city's art will deteriorate hopelessly within the next decade or so. Clearly, Venice is in peril. One headline proclaimed, "The Enemy's at the Gates."But for however long it lasts, Venice, decaying or not, will be one of the highlights of your trip through Italy. It lacks the speeding cars and roaring Vespas of Rome; instead, you make your way through the city either on foot or by boat. It would be ideal if it weren't for the hordes of tourists that descend every year, overwhelming the squares and making the streets almost impossible to navigate. In the sultry summer heat of the Adriatic, the canals become a smelly stew. Steamy and overcrowded July and August are the worst times to visit; May, June, September, and October are much better.Although Venice is one of the world's most enchanting cities, you do pay a price, literally and figuratively, for all this beauty. Everyone leaves complaining about the outrageous prices, which can be double what they are elsewhere in the country. Since the 19th century, Venice has thrived on its visitors, but these high prices have forced out many locals. They've fled across the lagoon to dreary Mestre, an industrial complex launched to help boost the regional economy.Today the city is trying belatedly to undo the damage that its watery environs and tourist-based economy have wrought. In 1993, after a 30-year hiatus, the canals were again dredged in an attempt to reduce water loss and reduce the stench brought in with the low tides. In an effort to curb the other 30-year-old problem of residential migration to Mestre, state subsidies are now being offered to the citizens of Venice as an incentive to not only stay, but also renovate their crumbling properties.The greatest plan to save "Venice in peril" is to place mobile barriers at the three entrances to the port of Venice. The plan, drawn up decades ago and debated ever since, would cost anywhere from $2 billion to $4 billion. A huge mobile sluice gate regulating the movement of the tides was tested as late as 1992. The catch is the final project would need 79 of these sluice gates to save Venice from its own waters.