Asberg, Mountain summit in Westerwald, Germany

The Asberg is a 428.5 m high hill on the Rheinwesterwald Volcanic Ridge, its blunt dome rising about 80 m above the surrounding plateau. Its summit lies in Unkel, with northern slopes in Rheinbreitbach and southern slopes in Erpel. Three water-filled quarry pits, covering two hectares in total, lie within 500 m west and east of the summit; the largest, eastern lake has silting zones.

From the late 1800s through the 1970s, the mountain served as a basalt quarry with a cable car system moving stone down to Rheinbreitbach below. This industrial period shaped the terrain and created the depressions that hold water today.

The name Asberg comes from "Asc", the ash tree, and may first have referred to the Celtic hillfort rather than the hill; locally it was once called "Ahsberg" and in the cadastre "Aasberg". The Rheinhöhenweg runs 1.5 km west of the summit and meets the path from there at a spot called Auge Gottes.

The summit is accessible via several hiking trails, and the former quarry pits serve as natural landmarks to help orient yourself along the routes. Visiting is possible year-round, though paths can become slippery during wetter months.

The basalt quarried here was cut into waterway stones and columnar basalt, carried down to the Rhine from 1886 on a 6.3 km cableway that cost 300,000 Reichsmark. Legal disputes with a rival quarry ended its operation in 1901, and it was dismantled from 1902.