Venice is divided into six ancient administrative districts, or 'sestieri'. And it boasts 118 islands gravitating around it. Some of these islands belong to sestieri, such as the island of Giudecca belongs to Dorsoduro or San Giorgio Maggiore belongs to the sestiere of San Marco. Also some islands are organised into sestieri, for example Burano has 5 sestieri. The Sestiere can definitely be considered an Italian district.
Visitors usually flock to St Mark's Square, focusing on the Basilica and the Doge's Palace. But each sestiere has its own attractions and beauties. The time spent exploring them will be well rewarded. Those coming to Venice should carve out at least four nights to get a real taste of the complexity of the place.
Keep in mind that getting around Venice is not that easy and takes time to settle in. There are no buses or taxis in Venice but waterbuses and water taxis. The Calle or Strade do not always have clear signposts and this often creates problems.
The organisation of Venice into sestieri was a necessity for organisation and control. And this model was exported to the areas of Venetian rule.
The Sestieri also appear in the directional iron of the Gondola, as six rectangular teeth, so much the pride of the Venetian boatmen.