Source: http://www.starwoodhotels.com/sheraton/property/area/map.html?propertyID=78

Approaching Venice by sea, Aschenbach passes through the city along canals, noting that he passes under the Bridge of Sighs.  After arriving near St. Mark's Square, he is taken to the barrier island called the Lido and stays at the Hotel Des Bains (Red Triangle) there. He travels regularly into Venice (Venezia) to see the sights and to keep track of his beloved Tadzio.

Hotel Des Bains, Venice Lido Resort

Lungomare Marconi 17 · Venice 30126 · Italy

You probably know that Venice is in the northeast corner of Italy, on the Adriatic sea. It is marked by a red star on the map below. Due north of Venice, the map also shows Munich, from which Ascenbach started his journey:

Source: http://www.mapquest.it/mq/maps/mapAddress.do?cboCountry=IT&region=EU&txtCity=Venezia&txtState=Veneto&txtLatitude=45.438049&txtLongitude=12.31822