A ruined medieval castle perched above the Ruhr River a few kilometres west of Witten, Hardenstein makes a natural destination for a walk or cycle along the riverfront. The ruins consist of a tower, sections of curtain wall, and the outline of the main building, set on a wooded promontory with views down the river valley.
The castle is freely accessible at all times. Combined with the Muttental trail and the Hohenstein park, it forms part of a circuit that can fill a full day of outdoor exploration around Witten without covering much of the same ground twice.