Lively Altstadt is the city’s historic heart, with cobblestone streets, centuries-old buildings, and bustling market squares overlooked by the hilltop Heidelberg Castle and gardens. Studentenkarzer is a graffiti-strewn former university prison, and the Deutsches Verpackungs-Museum displays product packaging and brand design. Main shopping street Hauptstrasse has bookstores, casual cafes, and traditional restaurants.