To be privately owned
The Castle can be visited
Herberstein Castle

Herberstein Castle, a historical complex, stands on a rock in the Feistritzklamm gorge. This feature provides the castle with protection and makes it inaccessible from three sides and barely visible from the outside.
History+
The origins of Herberstein Castle date back to the 12th century, when its oldest parts were constructed. Originally known as Herwigstein, the small castle was a fief of the Stubenberg family. Otto von Hartberg succeeded in converting this fief into free property and is since considered the ancestor of the Herberstein family. Around 1400, the complex was expanded with an outer bailey, which also included the Gothic St. Catherine's Chapel. In the 15th century, the outer bailey underwent further extensions. In the mid-16th century, the castle was transformed and expanded into a residential building with Renaissance elements. The Knight's Hall was built in the 17th century, and the deep moat was covered.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://en.wikipedia.org/wiki/File:Steiermark_Schloss_Herberstein_2.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: 47.2145, 15.8106