The Hauptstrasse runs right through the Altstadt from Bismarckplatz in the west to the Karlstor [de] in the east, with a slight bend following that of the Neckar river.

[1] It is crossed by numerous streets running from north to south (mostly called Gassen, "alleys") and there are five squares along its route.

One of these, the Marktplatz was planned as a market place from the beginning, while the other four - Anatomiegarten, Universitätsplatz, Kornmarkt, Karlsplatz [de] - were created through the demolition of buildings.

In the east, in the area of the modern Plankengasse, there was the German: Obere Tor ("Upper Gate"), which was replaced by the Karlstor in the 18th century.

[3] After the destruction of Heidelberg in the War of the Palatine Succession in 1693, the city was rebuilt in the baroque style, but retaining the old streetplan.

On 15 July 1972, the section from Universitätsplatz to Marktplatz was converted to a tram-only street and from 1 January 1974, it was also closed to all traffic on weekends.

[6] In addition to the shops and restaurants, there are several significant institutions, like the Town Hall, the Kurpfälzisches Museum, and parts of the University.