To be privately owned
Schönrath Castle

The Schönrath Castle Ruin, once a lowland castle, is situated in Lohmar in the Rhein-Sieg-Kreis, North Rhine-Westphalia. Only remnants of the main castle remain today.
History+
First documented in the 13th century, Schönrath was initially a knight's seat belonging to the Lords of Schönrode. The castle frequently changed hands, passing through noble families such as the von Landsberg, von Nesselrode, and von Quadt, before falling to the von Plettenberg family in the 15th century. In 1563, Diederich von Heyden managed to secure the castle for his family, who owned it for over a century. By the end of the 17th century, the castle was eventually sold to Baron Ernst von Erlenkamp. In the 19th century, the estate's value diminished due to the sale of associated farms.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Roland Neubert, Halle (Saale)
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: 50.8898, 7.2151