To be privately owned
Rantzau Castle

Rantzau Castle, in the municipality of Rantzau, Schleswig-Holstein, is a historic castle that once served as the ancestral seat of the noble Rantzau family. Although technically a manor house by definition, its significance in regional history has led to its designation as a castle. It experienced a brief period of prosperity in the late 16th and early 17th centuries as a Renaissance structure.
History+
The Rantzau estate has been inhabited for over 800 years. The name Rantzau suggests an earlier Slavic settlement. The Rantzau family, who adopted the name of their property, was first documented in 1226 with Johann von Rantzau. He founded the various lines of the family that shaped the history of Schleswig-Holstein. The estate remained in family possession for over 500 years. Under Heinrich Rantzau, the manor house was rebuilt starting in 1590. After Heinrich Rantzau's death in 1598, the castle largely belonged to the Breitenburg line of the family in the 17th and 18th centuries. Following its confiscation by Danish King Frederick IV in 1721, the estate changed hands several times.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://schloesserrundschau.de/schleswig/schloesser/ploen16.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: 54.2356, 10.5127