To be privately owned
Sprinzenstein Castle

On a 497-meter-high rock above the Kleine Mühl valley stands Sprinzenstein Castle, a castle complex in Upper Austria. Originally built as a castle in the 13th century, it was transformed into a Renaissance castle after a fire in 1583 and continues to shape the landscape near Sarleinsbach.
History+
The castle's origins date back to 1253, when Knight Siboto von Sprinzenstein, a Passau ministerialis from the Tannberg family, is mentioned as the first owner. After various changes of ownership, including Chunrad von Tannberg and Ortolf von Marsbach, the castle partially passed to Count Albrecht von Habsburg in 1281, thus becoming a princely fief. In 1369, Hans von Marsbach had a chapel built. Following further changes of ownership, including the Grans and Marspöck families, the Starhemberg cousins acquired the princely half in 1421. The second, Passau half went to Dionys Praun in 1525, who soon after owned the entire castle. After a fire in 1583, it was rebuilt into a Renaissance castle. Another fire around 1602 led to renewed reconstruction efforts, which shaped its current appearance by 1632.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Sprinzenstein_-_Schloss_8.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: 48.5478, 13.9436