Weilberg, Mountain summit in Königswinter, Germany

Weilberg is a 242.1 m summit in the Siebengebirge range within the Siebengebirge nature reserve near Königswinter. Its former quarry, closed since 1940, exposes a sequence of trachyte tuff, a red contact zone where magma baked the tuff, and a narrow basalt dike that widens in the soft tuff.

The mountain served as a source for basalt stone from the late 1800s onward, with extraction continuing until 1940. Material was transported across the region using a specialized railway system built to serve the mining operations.

On 15 October 1971 the Siebengebirge was awarded the European Diploma for Protected Areas; a memorial stone was set up at the Weilberg in 1974 to mark it. The hill lies in the middle section of the Siebengebirge nature reserve.

Several hiking routes lead to the summit, and sturdy footwear is recommended. Visitors should stay alert near the former quarry areas due to steep drops and uneven ground.

The quarry walls reveal a sequence rarely exposed in one place: trachyte tuff, a red-baked contact zone where magma burned the tuff, and a narrow younger basalt dyke that widens inside the soft tuff. Basalt was cut here in the 19th and early 20th centuries and carried down the valley on the Heisterbacher Talbahn.