The remains of the fortress can be visited
Kniepass Fortress

Kniepass Fortress, a historic defensive structure, is located in Tyrol, Austria. It once secured an important traffic route.
History+
The original redoubt at Kniepass was established at the beginning of the Thirty Years' War to protect the road between Reutte and Füssen. Its location, on a steep ascent next to a Lech gorge, made it ideal for defensive purposes. In 1632, the complex suffered partial damage, after which it was immediately rebuilt and reinforced, including a drawbridge and stone parapets. Further expansions took place in 1647 and 1670.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Sternschanze_Kniepass.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: 47.5284, 10.7053