The Ruprecht-Karls-Universität Heidelberg, founded in 1386 by Elector Ruprecht I, is the oldest university in Germany and one of the oldest in the German-speaking world. With around 30,000 students it remains a large and active research university, and its presence shapes the character of the entire city — the density of bookshops, cafés, and late-night bars on the Hauptstrasse and the lanes behind it is a direct result. Among the alumni and faculty over the centuries are an extraordinary roll-call: Hegel, Jaspers, Gadamer, and over fifty Nobel laureates.
The main places to visit are in the old town. The Alte Aula (Old Auditorium) on Grabengasse is the historic great hall of the university, built in the 1880s in neo-Renaissance style, with a painted ceiling and a gallery of former rectors' portraits; it can be visited as part of a guided tour or during open days. Nearby is the Universitätsmuseum, which traces the 600-year history of the institution through documents, instruments, and curiosities.
Perhaps the most visited university-related sight is the Studentenkarzer (Student Prison), a few steps away on Augustinergasse. From 1712 to 1914, students who committed minor offences — duelling, rowdiness, disturbing the peace — were sentenced to time in this small lockup. Rather than regard it as a punishment, generations of students treated it as a rite of passage, covering every surface of the cells with drawings, poems, and graffiti. The accumulated layers of student art are genuinely remarkable. The prison is now a small museum, open most mornings; entry is inexpensive.