The Isenburg is a ruined castle in the Western Ore Mountains between Hartenstein and the village of Wildbach in the town of Aue-Bad Schlema.

In the course of the settlement of the Ore Mountains, a fortifications was built on a rocky spur above the confluence of the Wildbach stream and the river Mulde.

The inner and outer shell is made of horizontal layers of brick, whilst the core is lined with cut stone laid in a herringbone pattern (opus spicatum).

The recommended way to visit the castle ruins is by foot from Hartenstein railway station which takes about 30 minutes.

The left-hand fork leads via a wild and romantic narrow path on top of the river bank of the Mulde to the same destination.