Here we are in front of the abandoned quarry at Mount Weilberg, close to Heisterbach Abbey at the L268 country road. On the signpost leading from the parking lot “Im Mantel” to the abandoned quarry you read “Geologischer Aufschluss” (geological outcrop).
In geology, an outcrop is a site where the rocks appear at the surface. So we see the geological structure there, which gives us an idea of how the Siebengebirge came into being. Moreover, there are information boards that explain (in German) in detail what happened about 30 million years ago.
Obviously, it was human activity that laid bare all these rocks. During the 19th and early 20th century, basalt was mined here, a stone that withstands even the greatest pressure. Due to the construction of roads and railways, the demand for basalt steadily increased.
Back then, there was a small railway line, the Heisterbacher Talbahn (Heisterbach Valley Railway). It ran between the villages Oberdollendorf and Niederdollendorf in the valley and Heisterbach Abbey and the quarries in the hills. During the week it transported stones and goods, on the weekends excursionists.
The friends of the model railway, in German “Eisenbahn- und Modellbahnfreunde Siebengebirge – EMFS” made a model of the quarry for the Brückenhofmuseum in Königswinter-Oberdollendorf. You can admire it in the museum or online at Brückenhof’s website www.brueckenhof.de, and there is a cool video on YouTube.
Diploma of Europe
The quarry at Weilberg was among the last to be closed. Finally, in 1922, the entire Siebengebirge region became a nature reserve.
Here on the Weilberg, on 15 October 1971, the Siebengebirge received the “European Diploma” for protected areas.
For more information see volcanic origin.