To be privately owned
Grünholz Manor

Gutshaus Grünholz is a manor house in Thumby-Grünholz, Schleswig-Holstein, distinguished by its long history and Baroque architecture. It embodies a piece of North German aristocratic culture and remains in private ownership to this day.
History+
The origins of Gut Grünholz date back to the Middle Ages, when it served as an economic court for the Bishops of Schleswig and was first mentioned in a document in 1463. In the 15th century, the Sehestedt family erected a small tower castle. Later, the estate changed hands multiple times through marriage and sale, including the Pogwisch, von der Wisch, and Ahlefeld families. In the 18th century, it came into the possession of the Brockdorff family, who had the current Baroque manor house built.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://de.wikipedia.org/wiki/Datei:Gut_Gr%C3%BCnholz,_Herrenhaus.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: 54.5770, 9.9502