To be privately owned
Merfeld Castle

In Dülmen-Merfeld is Haus Merfeld, a historic castle. It was the former seat of the Lords of Merveldt and later the Dukes of Croÿ, who also care for the Dülmen wild horses.
History+
The first documented mention of Merfeld as "Merfeldon" dates to around 890. The noble family von Merveldt first appeared in the 12th century, and a castle was first documented in 1358. A double castle was formed in 1394 and reunited in 1693. In 1316, the Lord of Merveldt secured rights to wild horses in addition to fishing and hunting rights. By the end of the 16th century, Adolf III von Merveldt came into conflict with the Holy Roman Empire and the Prince-Bishop of Münster. He established a free court at the castle and converted to Protestantism to defend his local rule. This line died out in 1691, and the estate passed to the von Merode family. After several changes of ownership in the early 19th century, Duke Alfred von Croÿ acquired the lands in 1836. Since the destruction of Dülmen Castle in 1945, Haus Merfeld has served as the residence for the Dukes of Croÿ.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://www.wehrbauten.de/thread.php?threadid=563
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: 51.8518, 7.2104