The remains of the castle can be visited
Alt-Heiligenberg Castle

The Alt-Heiligenberg castle remains, a former spur castle, are on a rock spur. The site was the ancestral seat of the Counts of Heiligenberg.
History+
Alt-Heiligenberg Castle was likely built in the 12th century by the Counts of Heiligenberg. The castle was first documented in 1163. In the mid-13th century, the counts constructed another fortification, Neu-Heiligenberg. Alt-Heiligenberg was not abandoned, as evidenced by mentions in 1307 and 1309. Archaeological finds, including pottery shards and a Celtic arrowhead, indicate a history of settlement.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Dietrich Krieger / CC BY-SA 3.0 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: 47.8277, 9.2952