To be privately owned
Schlüßlberg Castle

In the municipality of Schlüßlberg in the Grieskirchen district of Upper Austria, Schloss Schlüßlberg is located, a structure with medieval roots. It is now privately owned.
History+
The first mention of Schlüßlberg dates back to 1150, when Herwort and Walchun de sluzilberch were named as the presumed builders of a fortress. This complex originally served to secure access to the Trattnachtal valley. The Schlüßlberger family, who rose to knighthood in the 14th century, owned the castle until 1404. Subsequently, ownership changed hands multiple times, including to Erasmus von Hohenfeld in 1429, who had the Gothic chapel built. In the 17th century, the castle was converted into a palace under Seyfried Hager von Allentsteig. In 1668, Schlüßlberg came into the possession of the Barons von Hoheneck, who elevated it to a majorat in 1718. Through marriage and inheritance, the castle changed owners several times and is now in the hands of a private foundation.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Schl%C3%BC%C3%9Flberg_Schloss_Aussen.jpg?uselang=de
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: 48.2175, 13.8700