To be privately owned
Niederurff Castle

Niederurff Castle, a structure in the Schwalm-Eder district, once served as the ancestral seat of the Lords of Urff. Its exact construction date remains unknown.
History+
The first documented mention of the Lords of Urff dates back to 1160. Given that the fortified church of Niederurff was already documented in 1085, it is presumed that the oldest parts of the castle might date from the 11th and 12th centuries. In 1309, the castle was granted as a fief by Heinrich von Urff, his brother Conrad, and his sons to Count Heinrich IV of Waldeck. A condition was that the castle could not be used against the Hessian Landgraves in the event of conflicts between the Waldecks and the Landgraves. This agreement was reinforced in 1332 by a pledge to Landgrave Heinrich the Iron, who received the right to open the castle in times of war. There is no evidence whether the Landgraves ever exercised this option in their disputes with the Archbishopric of Mainz. It is also unknown whether Niederurff Castle was ever besieged or destroyed.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://www.wehrbauten.de/thread.php?threadid=1367
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: 51.0340, 9.1906