To be privately owned
Seehaus Castle

Seehaus Castle, a former medieval fortress, is situated on Lake Weidsee in the municipality of Petting. It is distinguished by its late Gothic chapel and was once a strategically important point for the Archdiocese of Salzburg.
History+
Originally, Seehaus was a medieval castle belonging to the Counts of Thann. Around 1280, it passed into the possession of Archbishop Rudolf of Salzburg. For the Archdiocese of Salzburg, the castle served as an important outpost on the “Lower Salt Road,” monitoring the transport of salt from Reichenhall and Berchtesgaden and enabling the collection of tolls. In 1479, the cost office and patronal court of Petting were moved to Seehaus, with the latter being dissolved in 1804.
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: 47.8996, 12.8207