To be privately owned
Bornheim Castle

Bornheim Castle is an elegant pleasure palace located in the Rhein-Sieg district of North Rhine-Westphalia. It captivates with its Baroque architecture and stands as a testament to the magnificent building art of the 18th century.
History+
Bornheim Castle was constructed between 1728 and 1732, with the Baroque master builder Johann Conrad Schlaun presumably providing the plans for this Maison de Plaisance. Of the earlier structures, only the outer bailey remained, while the former gate tower with its drawbridge completely disappeared. In its place, a Baroque entrance arch with a stone bridge and a small bell tower was erected. A major fire on February 4, 1972, destroyed further parts of the outer bailey, including the bell tower.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://www.zeche.org/
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: 50.7655, 6.9949