From the time it was built on a high, narrow peninsula above the rushing Aare, Bern's streets have followed the river's flow. The original town began by what is now the Nydegg Bridge—it controlled the ferry crossing there—and spread westward, uphill to the Zeitglockenturm (known locally as the Zytglogge), a clock tower constructed in 1191 to mark Bern's first significant western gate. Further expansion in 1256 stretched the city to where the Käfigturm now stands; one last medieval growth spurt, hot on the heels of a resounding victory over the Burgundians in 1339, moved the city walls west yet again to the present-day train station, the Hauptbahnhof.
The bustling, commercial city center radiates out from that train station. To get to the Altstadt, follow the trams across Bärenplatz and through the Käfigturm. Marzili and Matte, former working-class and still flood-prone neighborhoods, lie together along the riverbed of the Aare. All these areas are easily explored on foot, but in Marzili and Matte you may want to take your cue from the locals: walk down, ride the funicular up. The cluster of museums in Kirchenfeld, on the south side of the river, is a short (spectacular) walk or tram ride away.