The remains of the Castle can be visited
Heidenberg Castle (Ruin) (Obersaxen)

The Heidenberg ruin, a historic castle ruin, is on a rock head above the village of Tavanasa in Obersaxen, Graubünden, Switzerland.
History+
Due to a lack of written records, the exact history of Heidenberg Castle is difficult to reconstruct. However, archaeological findings suggest its construction in the 11th or 12th century. It is presumed that the castle was abandoned or only sporadically used as early as the 13th century, which could explain the absence of historical documents. The name "Heidenberg" might originate from the migrating Walser people, who referred to the decaying masonry as "ancient" or "pre-Christian," though the precise meaning of "-berg" remains unclear.
Source: Wikipedia · Licence: CC BY-SA 4.0
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: 46.7521, 9.0623