To be privately owned
Schellenstein Castle

In Olsberg-Bigge, North Rhine-Westphalia, lies Schellenstein Castle, a historic complex in the Hochsauerland district.
History+
The origins of Schellenstein Castle probably date back to 1183, with the first documented mention from 1270. Gerardus de Bigge is presumed to be the first owner. Towards the end of the 15th century, the castle passed into the possession of the Wrede zum Schellenstein family. Through the marriage of Otto Friedrich von Padberg to Anna Eva Maria de Wrede in 1664, the estate passed to the von Padberg family, who held it until the early 18th century before it was sold to Jobst Edmund von Brabeck.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://www.zeche.org/
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: 51.3585, 8.4636