To be privately owned
Lienzer Klause

The Lienzer Klause ruin is a fortress in East Tyrol, strategically located at a narrow point in the Drau Valley near Leisach. Although it was never directly besieged, it played a role in the Napoleonic Wars.
History+
The Lienzer Klause was first documented between 1241 and 1253 and belonged to the Bishops of Brixen. It served to protect their possessions from the Counts of Görz. After being taken over by the Counts of Görz and later by Tyrol, the Klause also became a court seat in the 14th century. Expansion took place in the 15th and 16th centuries, particularly for defense against the Ottomans. In 1661, following the termination of a truce, the fortress was modernized under Christoph and Elias Gumpp and reinforced with bastions. In the 18th century, the Klause lost significance, was abandoned in 1782, and offered for sale.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://www.wehrbauten.at
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: 46.7957, 12.7232