To be privately owned
Wisent Castle

In Lower Austria, Wisent Castle was built in 1571 under Valentin Polani and his wife Barbara, as evidenced by an inscription above the main gate. Initially mentioned as a fortress, it was transformed into a castle in the 16th century.
History+
The first documented mention of Wisent dates back to 1353. In 1514, a desolate fortress in Amelsdorf was sold, which was still mentioned in 1602. It is presumed that this was a different structure. In 1619, the castle was stormed and plundered by Buquoy's troops. Later, the estates of Mörtersdorf and Sachsendorf, along with the village of Limberg, were added to the Wisent dominion. In 1755, the castle came into the possession of Altenburg Abbey. Following a lightning strike in 1900 that caused a fire, the castle's second upper floor was removed, resulting in its current rectangular, single-story main building.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:GuentherZ_2011-07-09_0020_Amelsdorf_Schloss_Wisent.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: 48.5856, 15.7868