The Hexen Tower in Sarnen, now an archive depository, is one of the few remaining castle towers dating from the time of the formation of the Swiss Confederation.
Erected shortly before 1291, it came into the possession of Canton Obwalden in around 1308 in the wake of a non-violent conflict. Amongst other things, it then served as a prison, interrogation chamber, treasury, archive and museum. The 1985/86 restoration saw the alterations made over the centuries reversed, except for the 18th century structure, which was left intact and shown as a subsequent intervention. The installation of a lightweight, self-supporting skeletal framework made of steel has allowed the tower to be used as an archive without burdening the preserved original structure.