To be privately owned
Rufling Castle

In Leonding-Rufling, Upper Austria, stands Rufling Castle, a three-story castle situated on an artificial hill. Originally a medieval manor, it has undergone several transformations.
History+
The first mention of an estate at this location dates back to 791, when it was owned by Odalsalh von Rudolfvingen of Passau. In the 12th century, ownership changed hands frequently, including Otto and Hartwik Lengau, as well as Wilhering Abbey. After being granted as a dowry in 1215, the property reverted to relatives following tragic events. In the late 13th century, Rufling passed to citizens of Linz and later to Göttweig Abbey. From 1475, it was known as a knight's seat of the Stettner family and served as the seat of the Vicedominus from 1648. The list of subsequent owners is long and varied, including noble and bourgeois families, until it passed to the Wagenhofer family in 1916, remaining in their private ownership to this day.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Schloss_Rufling_-_Hofseite.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: 48.2767, 14.2147