To be privately owned
Roth Castle

Roth Castle, a historic estate in Rhineland-Palatinate, is now privately owned. Originally a commandery of the Knights Templar, it evolved into a castle.
History+
The first documented mention of the complex as a Templar settlement dates back to 1248. The cellars still originate from this early period. A stair tower was added in the 16th century, followed by a gatehouse in the 17th century. Under the aegis of the Knights Hospitaller, who later took over the complex, a new castle was built in 1733. After the destruction of World War II, the building was reconstructed in 1958. Roth Castle has been in private ownership since 1797.
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: 49.9230, 6.2231