The remains of the Castle can be visited
Château de Frœnsbourg

The medieval rock castle Château de Frœnsbourg, also known as Frönsburg, is situated in the Grand Est region of France. Its construction adapts closely to the natural rock formations.
History+
The first documented mentions of Frœnsbourg Castle date back to 1269, when it was named as property of the Frönsburg family. In the mid-14th century, in 1349, part of the ownership changed hands: Ludwig von Frundsperg acquired half, while Siegfried von Löwenstein and Reinhard von Sickingen each received a quarter. Just a few years later, in 1358, Count Palatine Ruprecht I became the feudal lord of the three owners. An event occurred in 1359, when Johann von Lichtenberg captured and destroyed the castle due to a breach of the public peace by its owners. Emperor Charles IV subsequently prohibited its reconstruction.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Fr%C5%93nsbourg_2006.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: 49.0369, 7.7433