Venice is a city-island which streets called "Calli" can be crossed only on foot. The only place people can arrive by car is Piazzale Roma after crossed the "Ponte della libertà" that connect Venice with the mainland.
The city centre is formed by 117 little islands connected by more than 410 bridges. Every time you cross a bridge you are changing island. The most famous canal is the "Canal Grande"
The Gran Canal starts in the point where Piazzale Roma and the train station are connected by the new Calatrava's bridge, and goes on until the San Marco Square passing thought the other three bridges that cross the Gran Canal: "Ponte degli Scalzi", Rialto bridge and "Ponte dell'accademia".
The city is divided is six "Sestieri": Cannaregio, Castello, Dorsoduro, San Polo, Santa Croce and San Marco. They are also divided by the Gran Canal; "de citra" on its right and "de ultra" on its left.