To be privately owned
Bullachberg Castle

Bullachberg Castle is a stately hip-roofed building with a round tower. It was built in 1905 on the eponymous hill in Schwangau by Eugen Drollinger (1858-1930) for the Munich entrepreneur Emil Papenhagen and acquired in 1927 by Rafael Prince of Thurn und Taxis, who lived here with his family until his death in 1996. Since then, the castle has been vacant but is not accessible to the public.
The Bullachberg is an elevation in the middle of the plain in front of the world-famous royal castles of Neuschwanstein and Hohenschwangau, which are each only about 1000 meters away. The castle has approximately 900 m² of living space and is architecturally inspired by Art Nouveau. It is a protected monument and houses, in addition to stately living rooms, a small chapel where services are still regularly held today.
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: 47.5671, 10.7334