Fenis / Hasenburg, early medieval-medieval castle ruin, Medieval castle ruin in Ins, Switzerland.

Fenis, also called Hasenburg, is a ruined hilltop castle on the Schlosshubel between Ins and Vinelz. Only earthen ramparts, terraces, the castle mound and traces of the moat remain; no masonry survives. The site is unusually large compared with other castles in the region.

Fenis Castle, also called Hasenburg, was a medieval hilltop castle from the 11th century, the ancestral seat of the barons and counts of Fenis. It stood on the Schlosshubel between Ins and Vinelz. An earthquake destroyed it in 1117. Earlier, a Hallstatt-period site occupied the same spot, linked to the burial mounds of Ins.

The name Fenis comes from the noble family that held the castle as its ancestral seat; Hasenburg, the alternative name, refers to the hare. The site lies on the Schlosshubel between Ins and Vinelz, where the earth ramparts and terraces remain visible in the landscape.

A hiking trail begins at Albert-Anker-Haus and leads to the ruins, with options to continue toward the Iron Age burial mounds and the UNESCO site of Luescherz. The route follows the terrain closely, so good footwear and reasonable fitness help you enjoy the walk.

The castle was destroyed by an earthquake in 1117, and no wall remains survive today; only earthen ramparts, terraces, the motte and traces of the ditch are visible. The site had earlier been occupied in the Hallstatt period, linked to the burial mounds of Ins.