The remains of the Castle can be visited
Heidenburg Castle

The Heidenburg castle ruin, also known as Herrenburg, is a hilltop castle whose origins are shrouded in mystery. It is on a spur of the Krämelberg above the Reichenbach valley in Rhineland-Palatinate.
History+
The exact construction period and the original name of the Heidenburg are unknown. The builder has also not yet been identified. Due to the use of Roman spolia, the complex was mistakenly considered a late Roman hilltop castle for a long time. However, finds suggest that the castle was built in the 11th or 12th century. In the 19th century, a large part of the castle hill was quarried away, significantly reducing the preserved remains. In 1885, the Historical Association of the Palatinate carried out a survey of the structures that were still present at that time.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Andreas Rockstein Kurpfalzbilder.de / Public domain via Wikimedia Commons
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: 49.5178, 7.5161