The Radegg Fortress ruins are on the south-facing slope of Rossberg in Osterfingen, on a rugged crag. By the west wall, where a boardwalk has now been installed, there probably was a drawbridge and a manor door leading into the building. The fortress was first mentioned in 1200. The lords of Rossberg owned goods in Osterfingen, Löhningen, Beringen, Guntmadingen and Trasadingen.

The fortress was probably destroyed around 1270, by battles with neighbouring gentry. The bow and crossbow arrows found in the outer bailey and the traces of fire illustrate the demise of the fortress.