Trams are a commonplace sight in most European cities thanks to the fact that these systems were put in place before the automobile became popular. As a result, you have a system which automobiles must adapt to, rather than the other way around. This is the primary reason why trams 'work' in Europe, but not in the United States.
While you're at it, take a look at the sidewalk. Not only are the streets cobblestoned, but many of the sidewalks are, as well, usually in black-and-white geometric patterns using 3cm-square cobbles.