To be privately owned
Panker Castle

Panker Castle, often referred to as a manor house, is a historic estate in Schleswig-Holstein with a history spanning over five hundred years. It is known for its well-preserved estate village, which today is an excursion destination.
History+
The origins of the Panker estate date back to the late Middle Ages when it came into the possession of the Rantzau family, a noble lineage in the region. Around 1650, the core of the current manor house was built. In 1739, King Frederick I of Sweden, from the House of Hesse, acquired the property to provide for his illegitimate sons, who established the Lordship of Hessenstein there. In 1808, the estate passed to the Electors of Hesse-Kassel and is now owned by the Hessian House Foundation.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://schloesserrundschau.de/schleswig/schloesser/ploen04.html
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: 54.3288, 10.5718