The remains of the Castle can be visited
Kapfenstein Castle (Ruin) (Küblis)

In the municipality of Küblis, the Kapfenstein ruin, also known as Ober-Sansch, stands at an elevation of approximately 1049 meters above the hamlet of Tälfsch. This castle complex in the Prättigau, Canton Graubünden, offers a glimpse into Switzerland's medieval history and its strategic importance.
History+
The first documented mention of Kapfenstein Castle dates back to 1275, when Walter von Vaz acquired it in an exchange from the deceased Heinrich von Kapfenstein. The Kapfenstein family is attested as early as the 13th century. In 1351, the heirs of Simon Straiff renounced their rights to the castle in favor of Count Friedrich von Toggenburg.
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: 46.9218, 9.7756