Wartenstein Castle, Medieval castle ruin in Lauperswil, Switzerland.

Wartenstein Castle is a ruin on a narrow ridge of the Hundschüpfen above Lauperswil, surrounded on three sides by ditches. The southern plateau held a tower, courtyard and great hall; the east side had a zwinger and a well. Today the site is wooded, with tower remains and foundation walls visible.

The castle was held by the Swaro von Wartenstein family from 1228. In 1284 Heinrich Swaro sold it to Trub monastery and received it back as a fief. In 1383 Bernese troops captured and burned it during the Burgdorferkrieg. The ruins passed to Ulrich von Balmoos in 1415 and were excavated and repaired in 1965.

The site attracts hikers interested in exploring remnants of medieval fortification. The layout on the hillside shows how castles of this period were built to fit into the landscape.

A marked hiking trail from the hamlet of Blindenbach leads visitors through the forest to the castle ruins in about 20 minutes on foot. The terrain is hilly and can be slippery when wet, so sturdy hiking boots are recommended.

The castle well, or Sodbrunnen, lay on the east slope, where traces of a building remain. Local legend holds that during the Bernese siege the last lord threw his treasure into this well and then fell to his death with his daughter and horse. A large castle dog is said to guard the treasure and drink at Lauperswil's church fountain when the bell strikes one.