To be privately owned
Lower Castle Antweiler

The Lower Antweiler Castle, also known as Unterburg Antweiler, is a moated castle situated on the northeastern edge of the Eifel. It is located in Mechernich-Antweiler in the district of Euskirchen.
History+
The origins of the Lower Antweiler Castle date back to the 13th century, when it was presumably built by the bailiffs of Deutz Abbey and Dietkirchen Collegiate Church in Bonn to secure their rule. In 1345, the Lords of Antweiler received jurisdiction from the Count of Jülich, which led to the development of the sub-lordship of Antweiler. In the 15th century, the Lords of Metternich were the owners, simultaneously serving as hereditary bailiffs for both ecclesiastical institutions. At the end of the 15th century, specifically in 1488, the Lords of Ahr acquired the bailiwick and lordship.
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: 50.6061, 6.7448