The remains of the Castle can be visited
Grimmenstein Castle (Ruin) (Wynigen)

East of Wynigen in the Emmental, Canton of Bern, Switzerland, the Grimmenstein ruin is located on a rocky ridge above the Kappelenbach. The former 13th-century hilltop castle served as a strategic control point.
History+
Grimmenstein Castle was built in the 13th century and was the ancestral seat of the Lords of Grimmenstein, documented between 1271 and 1381, who served the Kyburgers. Its primary function was to secure the elevated route connecting Willisau with the Emmental. In 1383, during the Burgdorf War, the castle was besieged by Bernese troops. The then lord of the castle, Petermann von Rohrmoos, surrendered the fortress to the Bernese, receiving Bernese citizenship rights and the castle back as a fief in return.
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: 47.1064, 7.6944