To be privately owned
Arloff Castle

In the Arloff district of Bad Münstereifel in North Rhine-Westphalia, Arloff Castle, a former moated castle, is situated on the Erft River. Although it appears rather inconspicuous today, it is one of the typologically significant castles in the Rhineland, as it represents a rarely clearly preserved, purpose-built defensive structure from the early Gothic period.
History+
Arloff Castle was first documented in 1278. At that time, it was owned by Gerlach von Dollendorf, whose family, the Nobles of Dollendorf, were among the oldest and wealthiest noble families in the region. Gerlach enfeoffed the castle and its associated lands to Archbishop Siegfried of Cologne. Ten years later, after the Battle of Worringen in 1288, the balance of power shifted. The Counts of Jülich, who were on the winning side, became the new liege lords. To avoid disputes, a compromise was reached: the respective owner of Arloff Castle was invited to the diets of both principalities, Cologne and Jülich. This agreement lasted for over 500 years.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://www.wehrbauten.de/thread.php?threadid=568
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: 50.5926, 6.7870