One of the first things that Aschebach sees upon his arrival in Venice is the Bridge of Sighs.  According to Wikipedia, the Bridge of Sighs connects the old prisons of Venice to the interrogation rooms of the Doge's Palace.  This seems symbollically important to understanding Aschenbach's arrival in Venice, as he is already disappointed by the rainy weather during his approach.  As he usually approaches Venice by land, he ordinarily does not pass under this bridge.