To be privately owned
Galkhausen Manor

In Langenfeld, North Rhine-Westphalia, Gut Galkhausen is a manor and estate house, considered one of the oldest settlement sites in the region. It was recognized as a cultural monument in 2005.
History+
The first documented mention of Gut Galkhausen dates back to 1347. Around 1440, it appeared in a document from Altenberg Abbey in connection with a land transaction. Around 1442, the estate was owned by the Soutmann family, who exchanged it for farmland, at which point the property's condition was described as "unbuilt and desolate." In 1466, the estate was acquired by the von Etzbach family through purchase, and in 1829, it passed into the possession of Baron Johann Wilhelm von Mirbach zu Harff. From 1897, the grounds were used for the construction of the "6th Provincial Asylum," now a hospital.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://www.wehrbauten.de/thread.php?threadid=583
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: 51.0971, 6.9638