To be privately owned
Nienover Castle

Nienover Castle is in the municipality of Bodenfelde in the district of Northeim, Lower Saxony, Germany. It developed from a medieval castle complex to its current status as a private estate.
History+
The origins of Nienover date back to the first millennium, when a Romanesque castle complex was built here, first mentioned in 1144. After Henry the Lion's imperial fief was withdrawn, the castle passed to the Counts of Dassel, who moved their main residence here around 1200. In 1303, the complex was sold to Duke Albrecht II and served the Dukes of Braunschweig for a long time as a hunting residence.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: https://commons.wikimedia.org/wiki/File:Nienover_Schloss.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: 51.6808, 9.5229