To be privately owned
Schallmauer Castle (Berrenrath)

On the northern edge of the Hürth district of Berrenrath is Burg Schallmauer, a Baroque manor house. Built in 1714, it is one of the few structures that survived the demolition of the former village of Aldenrath. Its name is derived from the noble family Schall von Bell, who once owned moorland in this area.
History+
In the mid-16th century, Friedrich von Sachsen-Lauenburg, a canon from Cologne and Bremen, had a small country house built on this site for the Cologne canons. However, this castle was destroyed in 1673 by Dutch troops during the Dutch War.
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: 50.8823, 6.8150