The ruins of Rudenz Castle stand on a hill above Brünigstrasse. The highest preserved walls are a good 4 metres in height and 1.80 metres thick at the base.
The edifice was a simple tower castle occupying a hilly outcrop overlooking the village to the east. On the mountain side, it may have been protected by a ditch, otherwise there exist no other signs of fortification. The walls are fashioned from layered blocks of stone, some of considerable size; the corner stones are chiselled. The tower must originally have been accessible via a high entrance
and was probably built around 1200. It started out as the seat of the Rudenz family, who came from the Hasli valley. They extended their rule in Obwalden and established links with the nobility of Uri, the barons of Attinghausen. The Rudenz sold their property between 1361 and 1366 and moved to Uri, but the tower continued to be inhabited until the 16th century.
It's not known when the edifice was abandoned, but its stones were used as building material in later centuries. Excavations were carried out on the castle hill as early as 1850, during which arrowheads, lance heads and stirrups came to light. Similar finds were made in 1887 when the Brünig Railway line was laid behind the castle.