The castle ruin Valcastiel (also called Valkastiel) is the ruin of a medieval castle on a hilltop near Vandans in the Austrian state of Vorarlberg.
Not much is known about the history of this extremely exposed ruin.
For a long time it was assumed that the Montafon castle, mentioned in 1391 and documented in the archives, was probably destroyed in 1405 in the Appenzeller War. According to other findings, the Montafon castle does not refer to a building, but should be considered a medieval rulership designation.
Above the village of Vandans is the Valcastieltobel with the Mustergielbach between the Geißberg and the Fahrengrat. The ruin stands near the western end of a sharp rock ridge that rises very ruggedly between the Mustergielbach in the south and a tributary of the Valkastieltobel in the north that rises to the Vandanser Steinwand. It can be reached from Vandans via a marked hiking trail, mostly along a forest road, which leads to the base of the ridge. The last part goes over steep wooden steps and a path secured with steel cables. Shortly before reaching the rock outcrop, as the bridge has broken down, the Mustergielbach must be crossed, which can be difficult if the water is strong.