Burg Mühlenbach, Medieval castle ruins in Koblenz, Germany

Burg Mühlenbach is a ruined lowland castle in Koblenz-Arenberg, of which only the main tower survives. The five-storey tower is 23.5 m high, built of greywacke rubble on a square plan and topped by a tent roof. Some slit windows, a south-side stair to a first-floor door with a pointed-arch blind niche, and parts of the medieval plaster remain.

Hermann II von Helfenstein commissioned this castle around 1300, establishing it as an important fortification in the region. By the 14th century, it came under the control of the House of Brandenburg.

The tower displays traces of medieval life through ancient chimney structures discovered inside its walls. These remains offer glimpses into how castle residents lived in those times.

Visiting requires a walk through the forest to reach the ruins located near the source of the Mühlenbach river. Wear appropriate footwear since the path is natural and can be muddy in places.

The preserved main tower served as a grain store in the early 20th century, long after the castle's military role ended. Since 2002 it has been part of the UNESCO World Heritage Upper Middle Rhine Valley.