The Grand Canal in Venice is the easiest way to get around Venice. It basically divides the city down the middle, with most taxi and bus services running on it.
There are only four bridges that you can use to cross the canal, however it is a small city; so you never really find yourself stuck on the wrong side of the canal. Venice is remarkably compact, you can easily cross it on foot in less than an hour, and by using the water-bus (Vaporetti) in about 1/2 hour.
Although it is difficult to get an original shot of the canal that has not been taken 100 times before, it is truly a beautiful location for some great shots.