About three days is ideal:
- Day 1: the main sights around San Marco and the Rialto Bridge.
- Day 2: a boat trip to Murano (glass-making) and Burano (colourful houses).
- Day 3: the quieter districts such as Cannaregio, Castello and Dorsoduro, plus lesser-known spots.
With only one day, focus on San Marco and Rialto and go early to beat the crowds.