To be privately owned
Deutsch-Nienhof Manor

The Deutsch-Nienhof Manor House in Schleswig-Holstein evolved from a moated castle to a manor house, remaining in private ownership to this day.
History+
The first documented mention of the Deutsch-Nienhof estate dates back to 1472. In the early 16th century, the property came into the possession of the Rantzau family, who constructed a three-winged moated castle on the site. This castle is depicted on the Rantzau Panel. The current manor house was built at the end of the 18th century on the foundations of this earlier moated castle and underwent redesigns. A gatehouse designed by Georg Greggenhofer, originally intended for Deutsch-Nienhof, was only realized approximately 200 years later at the Molfsee Open-Air Museum.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://schloesserrundschau.de/schleswig/schloesser/rendsburg33.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: 54.2533, 9.9152