The remains of the Castle can be visited
Hardenburg Castle

Hardenburg Castle Ruin is located above the Hardenburg district in Bad Dürkheim. Its strategic location on the eastern edge of the Palatinate Forest once allowed it to control the Isenach Valley and its access to the Rhine Plain.
History+
The Counts of Leiningen built Hardenburg Castle between 1205 and 1214, unlawfully appropriating land belonging to Limburg Monastery. Count Friedrich II of Leiningen is considered its founder. Following a division of inheritance in 1237, the castle passed to Count Friedrich III. Another division of inheritance in 1317 led to the establishment of the Leiningen-Hardenburg line under Count Jofried. In 1512, after the imperial ban against Count Emich IX, Hardenburg was besieged by Elector Ludwig V of the Palatinate, but surrendered without damage and was returned in 1519. In the late 15th and early 16th centuries, the castle was expanded and reinforced to protect it against artillery fire.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Dr. Gebhard Gaukler
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 49.4622, 8.1217