Venice spreads over 159 square miles on two different environments,land and water.
On the mainland there are 10 boroughs of which the industrial and commercial centres of Mestre and Marghera are the largest.
At a distance of about 2.48 miles from the mainland and built on some 118 islands there is
Venice: the city since the 12th century has been divided in six main districts or sestieri,three on
both sides of the Grand Canal which divides Venice into two irregular halves.
Looking on your map,Dorsoduro,Santa Croce and San Polo are on the left bank of the Grand Canal while San Marco, Castello and Cannaregio are on the right bank.
Part of Venice as well ,the Giudecca is a formation of eight islands separated form the main built up area by the largest and deepest water way leading to the city's port.
Overlooking the Adriatic Sea and extending along narrow strips of land and sand the two elongated islands of Lido and Pellestrina separate the lagoon from the open sea which flows into the lagoon's basin trough three wide port mouths.
Besides the Venetian archipelago other island cities exist on the lagoon 's 106 square miles of brackish water,most notably Murano,Burano and Torcello located north of Venice.
The total population in the City Council of Venice is 270.733 people of which 180.200 reside in the mainland, 60.187 in the six original Venetian districts and 30.289 on the beach strips of Lido and Pellestrina and the islands of Murano and Burano.
(updated May 2009)