To be privately owned
Hohlenfels Castle

Hohlenfels Castle, a rock castle in Rhineland-Palatinate, is located in the municipality of Mudershausen in the Rhein-Lahn district. It is a privately owned, inhabited property that is occasionally opened for events.
History+
The history of Hohlenfels Castle began before 1353, when Count Johann I of Nassau-Weilburg-Saarbrücken commissioned its construction by Daniel von Langenau. Its strategic location was intended to control important trade routes, which, however, triggered a feud with the Counts of Diez. An arbitration ruling in 1353 confirmed the rights of the Diez family, and an agreement was finally reached in 1363: the castle remained a Nassau fief, but the Diez family was granted the right of access. After the death of Daniel's son Hildeger von Langenau in 1412, the castle was divided among his descendants and developed into a joint inheritance castle. In the 16th century, it came into the sole possession of the Lords of Mudersbach. After the death of Daniel von Mudersbach in 1600, his son-in-law Hartmut von Kronberg was enfeoffed in 1604. During the Thirty Years' War, the castle was partially destroyed and abandoned, but was reoccupied in 1685 by Johann Nikolaus von Kronberg.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://de.wikipedia.org/wiki/Datei:Burg-Hohlenfels-JR-G6-3645-2009-08-04.jpg
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: 50.2904, 8.0310