The remains of the Castle can be visited
Balcun At Castle

The castle ruin of Balcun At overlooks the Val Müstair in Graubünden, Switzerland. These sparse remains of a former hilltop castle are situated high above the valley floor.
History+
The exact construction period of Balcun At Castle is not recorded, but archaeological findings suggest it was built in the 12th or 13th century. Its size and strategic location directly above the episcopal monastery of Müstair suggest it was erected with the bishop's consent, possibly by his retainers. The name Balcun At, later Germanized to Hohenbalken, first appeared in 1427 and may refer to a high-lying balcony or gallery. There is also no definite information about the castle's destruction; traces of fire indicate a blaze, but a collapse or destruction during the Bündner Wirren are also conceivable.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://de.wikipedia.org/wiki/Datei:Balcun_At_Nordecke.jpg
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: 46.6250, 10.4605