The island of Giudecca's name is something of a mystery. It may come from a possible 14th-century Jewish settlement, or because 9th-century nobles condemned to giudicato (exile) were sent here. It became a pleasure garden for wealthy Venetians during the Republic's long and luxurious decline, but today it's populated by a combination of working-class Venetians and generally expatriate gentrifiers. The Giudecca provides spectacular views of Venice. Thanks to several bridges, you can walk the entire length of its promenade, relaxing at one of several restaurants or just taking in the atmosphere.
You can reach the Giudecca via vaporetto Line 2 from San Zaccaria. After San Giorgio Maggiore, the next stops on the line take you to the Giudecca, crossing over to the Zattere in Venice proper between the Giudecca stops. The island's past may be shrouded in mystery, but today it's about as down to earth as you can get, and despite substantial gentrification, it remains one of the city's few essentially working-class neighborhoods. The view of Venice from the rooftop bar at the Hilton hotel (Molino Stucky—it used to be a 19th-century flour mill) is perhaps even more spectacular than the view from San Marco’s Campanile.