The 121 islands of central Venice are divided into six districts known as sestieri, and the houses within each sestiere are numbered in a sequence that makes sense solely to the functionaries of the post office – this explains how buildings facing each other across an alleyway can have numbers that are separated by hundreds.
Venice’s main thoroughfare, the Canal Grande, divides the city in half – three sestieri to the west and three to the east. On the east side of the Canal Grande is the sestiere of San Marco, the area where the majority of the essential sights are clustered, and accordingly the most expensive and most crowded district of the city. East of San Marco is Castello, and to the north is Cannaregio – both of which become more residential, and quieter, the further you get from the centre. On the other side of the Canal Grande, the largest of the sestieri is Dorsoduro, stretching from the fashionable quarter at the southern tip of the canal to the docks in the west. Santa Croce, named after a now-demolished church, roughly follows the curve of the Canal Grande from Piazzale Roma to a point just short of the Rialto, where it joins the smartest and commercially most active of the districts on this bank – San Polo.