To be privately owned
Montplaisir Castle (Roter Bau)

In Niederwürzbach, a district of Blieskastel in the Saar-Pfalz-Kreis, lies Montplaisir Castle, also known as the Red Building. It is part of a baroque ensemble that was once laid out around the Würzbacher Weiher.
History+
In the last quarter of the 18th century, the Counts of der Leyen had several small castles and country houses built near their residence in Blieskastel. Montplaisir Castle was constructed between 1785 and 1786 as a country house for Countess Maria Anna. The construction was carried out by court architect Peter Reheis and incorporated a mill core that had existed since the Middle Ages. The bel étage served as the Countess's residence.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: https://commons.wikimedia.org/wiki/File:Schloss_Monplaisir_%28%E2%80%9ERote_Bau%E2%80%9D%29_in_Niederw%C3%BCrzbach.jpg
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: 49.2443, 7.1923