Klusenstein Castle, Medieval castle in Hemer, Germany

Klusenstein Castle is a stone fortress perched on a 60-meter limestone cliff overlooking the Hönne river valley and a narrow passage below. The structure includes a timber-framed barn from the 18th century that once housed livestock.

The castle was built in 1353 by Gerhard of Plettenberg as a border fortification between the territories of Mark, Cologne, and Arnsberg. It controlled a strategically important position along a key regional trade route.

The castle structure includes a timber-framed barn from 1749, which was used as a cattle house and underwent restoration for its 650th anniversary.

The castle is owned by Rheinkalk and leased out, so the grounds are not open to visitors; the buildings can be seen from the public paths and roads around the Hönne valley. The Balve–Menden railway, running since 1912, passes directly below the cliff.

The cave beneath the rock is 51 metres long in total. One corridor bends upward but is blocked by stones about 30 metres below the plateau. In 2003 the upper entrance was found below the eastern palais, which was destroyed in 1840.