The Hardenburg on the eastern edge of the Palatinate Forest near the Rhineland-Palatinate town of Bad Dürkheim is even as a ruin one of the mightiest castles of Palatinate.
Wikipedia https://en.wikipedia.org/wiki/Hardenburg_(Bad_Dürkheim)
Address Bad Dürkheim 67098, Germany
Coordinates 49°27'43.887" N 8°7'19.265" E