Alt-Wartburg ruin, Medieval castle ruin in Oftringen, Switzerland

Alt-Wartburg is the ruin of a hilltop castle on the Säli, a sub-peak of the Engelberg chain at 632 m above sea level, in the municipality of Oftringen. Only about 150 metres to the north stands the Neu-Wartburg, also called Sälischlössli, which lies in the municipality of Starrkirch-Wil. The site is a class A Swiss cultural property of national significance.

The lords of Ifenthal built the original castle at the end of the 12th century and expanded it during the early 13th century. This growth period shows how the family gained more influence in the area over time.

The name Wartburg refers to a watch castle, and the site's paired fortresses reflect that role: the Ifenthal family built Alt-Wartburg and later Neu-Wartburg just 150 metres north, on Starrkirch-Wil soil. The Hallwyl family, owners from 1379, rebuilt Neu-Wartburg after 1415 but let Alt-Wartburg decay, which is why only this ruin survives.

The ruins are easy to reach from Oftringen on well-marked hiking trails that take about one and a half hours from nearby Olten station. Visit on dry days when the paths are firm and you can move safely around the rocky terrain.

Excavations in 1966 and 1967 uncovered broken pieces of tiled stoves and clay floor tiles in the fire layer left by the Bernese troops in 1415. These finds show that the castle had heated living rooms before it was abandoned.