The remains of the Castle can be visited
Leonstein Castle

The castle ruin of Leonstein is situated high above Lake Wörth in Carinthia. The complex in the northwest of Pörtschach am Wörther See gives insight into the development of defensive structures.
History+
The first documented mention of Leonstein Castle dates back to 1166, when it was owned by the Leonsteiner family. The castle later changed hands, passing to the Erolzheim and Peuscher families. In 1431, the complex was sold to Thomas and Ludwig von Rothenstein, briefly entering the possession of the Swabian noble family of Rothenstein. By the 17th century, the castle had already fallen into ruin, as documented by a depiction from Valvasor in 1680.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Poertschach_Burgruine_Leonstein_28112013_333.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: 46.6390, 14.1292