Auenstein Castle, Medieval castle in Auenstein, Switzerland

Auenstein Castle is a stone fortress perched on a rocky hill above the Aare river, displaying architectural features from its 13th-century foundation and 1920s modernization work. The structure features thick stone walls and a compact form characteristic of medieval defensive buildings, with some areas now adapted for modern use.

The castle was built in the 13th century, probably for the Lords of Gowenstein, and was first documented in 1307 as property of the Lords of Reinach. In 1389 Bernese troops stormed and burned it during Habsburg–Confederate fighting, and it stayed a ruin for centuries. In 1858 it was made habitable again and rebuilt as a castle, with a further addition in 1928.

The castle takes its name from the village of Auenstein, whose lordship was tied to the ruin and changed hands with it. Albrecht von Rinach sold the ruin and the surrounding villages to Heinrich Hasfurter of Lucerne in 1465, so ownership of the walls and of the village went together. The Reller family, owners since 1970, moved a real estate company into the building in 2009.

The castle sits on elevated ground with good views over the surrounding landscape and the Aare river below. Access is on foot from the village of Auenstein via a footpath, and sturdy footwear is recommended since the terrain can be uneven.

After centuries as a ruin, the castle underwent complete reconstruction in the 1850s, transforming from decaying walls into a livable residence. This rebuild fundamentally changed its character and saved it from disappearing entirely.