Towering over the Altstadt, Heidelberg’s ruined Renaissance castle cuts a romantic figure, especially across the Neckar River when illuminated at night. Attractions include the world's largest wine cask and fabulous views. It's reached either via a steep, cobbled trail in about 10 minutes or by taking the Bergbahn (cogwheel train) from Kornmarkt station. The only way to see the less-than-scintillating interior is by tour, which can be safely skipped. After 6pm you can stroll the grounds for free.
Once you arrive up top, you'll be struck by the far-reaching views over the Neckar River and the Altstadt rooftops. Show your ticket to enter the Schlosshof, the castle’s central courtyard, which is framed by reconstructed Gothic and Renaissance buildings with elaborate facades. The most eye-catching belongs to the Friedrichsbau, which is festooned with life-size sculptures of kings and emperors.
You can't miss the Grosses Fass, the world's largest wine cask, with a capacity of about 228,000L. Also worthwhile is a spin around the surprisingly interesting Deutsches Apotheken-Museum.