To be privately owned
Wallsee Castle

In Lower Austria, Wallsee Castle is situated above the Danube. This former stately home in Wallsee-Sindelburg once served as the residence of an imperial princess.
History+
The history of Wallsee Castle is tied to the local economy, a connection that lasted from the Middle Ages until the early 1920s. An era began in 1895 when Archduchess Marie Valerie, daughter of Emperor Franz Joseph and Empress Elisabeth, acquired the estate with her husband, Archduke Franz Salvator. They purchased the castle on June 11, 1895, from Duke Alfred of Saxe-Coburg and Gotha and had it renovated. Following the completion of the works, they made an entrance into their new home on September 4, 1897. In 1918, their daughter Hedwig married Count Bernhard zu Stolberg-Stolberg at Wallsee Castle.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: https://commons.wikimedia.org/wiki/File:Wallsee_Schloss_2.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: 48.1698, 14.7149