To be privately owned
Ahausen Castle (Heggen)

In the Bigge Valley, Ahausen Castle is a complex built on the foundations of a former moated castle. This structure is a defining feature of the region.
History+
The first documented mention of the locality Ahausen dates back to 1313 and 1338, when Count Gottfried IV of Arnsberg granted milling and fishing rights to the von Heygen family. In 1363, ownership passed to the Lords of Schnellenberg, whose branch of the family adopted the suffix “van Aehusen”. Johan and Gerlach von Aehusen mortgaged the estate to the city of Attendorn in 1428, but redeemed it in 1431. After several changes of ownership, Johann Moritz von Schade zu Grevenstein acquired the property in 1642. He had the estate rebuilt, with the outbuildings and manor house constructed in 1676.
Source: Wikipedia · Licence: CC BY-SA 4.0
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: 51.1416, 7.9546