Atop a forested Pfälzerwald hill 6km southwest of the centre, this 'cradle of German democracy' is where idealistic locals, Polish refugees and French citizens held massive protests for a free, democratic, united Germany on 27 May 1832, hoisting the black, red and gold German flag for the first time. An exhibition commemorates the event, known as the Hambacher Fest. Audioguides and 45-minute guided tours are available in English. Bus 502 (17 minutes, hourly) runs from the Hauptbahnhof.
Other tours include architecture, children's tours, and tours for the visually impaired. There's a restaurant at the castle.