To be privately owned
Kerpen Castle

Kerpen Castle, a spur castle, stands on a dolomite spur in the Volcanic Eifel region. Located in Kerpen, Rhineland-Palatinate, it has a history marked by noble families and ownership disputes.
History+
The exact origins of Kerpen Castle are unknown, but its construction is attributed to Sigibertus de Kerpene or his son Heinrich I, who were documented in the 12th century. In 1265, the castle was enfeoffed to Archbishop Engelbert II of Falkenburg of Cologne. Later, Theoderich II and his brother Wilhelm II shared ownership. Theoderich III, mentioned in 1299, was the progenitor of three lines that jointly owned the castle as a Ganerbenburg (a castle owned by multiple families). Konrad von Kerpen-Mörsdorf sold his share to Wilhelm II von Sombreff in 1346, who acquired further shares in 1448, eventually becoming the sole owner. After his death, ownership disputes lasting over 200 years erupted. Through the marriage of Wilhelm's sister Margarete to Count Dietrich von Manderscheid-Schleiden, the castle came into the possession of this comital family. Dietrich IV had a Gothic castle chapel built in the early 16th century. After his childless death in 1593, Philipp von der Mark occupied the castle to assert ownership claims. A settlement in 1611 ended this dispute.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://www.wehrbauten.de/thread.php?threadid=2041
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: 50.3112, 6.7322