Venice is divided into six sestieri (districts) spread across several islands in the lagoon between the coast of Italy and the Adriatic Sea. Protected from the sea by a number of barrier islands, the city has been by turns sinking, decaying and flooding for centuries.

The sestieri also are the foundation of Venice's confusing address "system," which does not follow streets but the district itself, making getting around more difficult than other cities. Most visitors will spend a lot of time in the districts of San Marco, San Polo and Dorsoduro, where the main sights are found. This means throngs of tourists clogging the narrow streets and alleys, but it also means a relatively compact area for travelers with limited time to visit the city. Running through the city is the Grand Canal, which is the main transportation artery since everything and everyone in the city travels by boat. Numerous canals branch off in every direction, many with tiny bridges over them, making walking even short distances more of a meander - and definitely good exercise.