Ruins Schönenwerd, Castle ruin in Dietikon, Switzerland.

Ruins Schönenwerd is a medieval castle site near Dietikon with preserved stone walls and foundations sitting on elevated ground. The remains show the layout of residential buildings and defensive structures that reveal how people organized the settlement.

The castle emerged during the medieval period as a fortification to control trade routes in the region. The site was later abandoned and today only its foundation walls remain visible.

The castle was built on a Limmat island, and the river has since shifted about 200 metres east of the ruins. The knights of Schönenwerd, first documented in 1240, held bailiwick rights over Dietikon-Oberdorf and owned land along the Reppisch. In 1257 they promised Zurich not to sell land across the river for a bridge.

The ruin lies about 200 metres from the left bank of the Limmat and 600 metres east of Glanzenberg SBB station on the Zurich–Baden line. The remains of Glanzenberg castle and town stand on the opposite bank, roughly 700 metres downstream. The site was excavated by Karl Heid in 1930–35 and conserved by the Zurich building office in 1970/71; it belongs to the town of Dietikon.

Excavations at the site unearthed metal objects and pottery fragments from different periods of castle occupation. These findings provide clues about how long the fortification was inhabited and used.