The ruins of Hohenburg Castle stand on the Schlossberg above town. The castle began as the seat of the counts of Homburg, was later reshaped into a fortress, and still gives the hill a sense of why the town grew below it.
The remains are not as complete as Germany's showpiece castles, but the setting is strong. Visit before or after the caves and use the hill for views over Homburg and the surrounding Saarland countryside.