Papenkaule Volcanic Crater

"... The Papenkaule is an 80 meter wide and 20 meter deep circular volcanic crater and is now a valuable geotope and biotope. The Papenkaule is a celebrity throughout the Eifel and something very special.
Around 10,000 years ago it became loud and uncomfortable for the Stone Age residents who had settled in the Buchenloch cave on the former sea reef of the Gerolstein Dolomites. A volcano broke through the limestone cliffs in their immediate vicinity. The Papenkaule was created - not a high arching volcanic cone with a crater in the summit, but a depression in the bedrock that still exists today.

Lava flow with a difference...
The lava emerged 300 meters west of the explosion source in the Hagelskaule and flowed south into the Kylltal in the direction of today's Gerolstein district of Sarresdorf. This sideways movement of the lava flow is unique in the UNESCO Volcanic Eifel Nature and Geopark and arose because the karst rock massif has underground cracks through which the flow of embers reached the surface horizontally rather than vertically.
Due to the nature of its soil, the Papenkaule never became a water-filled maar or crater lake. The limestone, which was formed by the death of countless lime-forming organisms and other marine animals in a subtropical shallow ocean 380 million years ago, is far too porous. The hollow in the reef is a habitat for rare animals and plants that thrive on limestone grassland. For hikers on the Eifelsteig or on its partner path, the Felsenpfad, who enjoy their stage on the Gerolstein Dolomites, the place is above all a place to pause, take a deep breath and find peace. ..."
geopark-vulkaneifel.de/eifel/landschaft/ausfluege-in-die-erdgeschichte/papenkaule.html

The Papenkaule is a former volcano, the lava of which, however, did not come to light here when it erupted, but at the hailstones about 300 meters away.

It's exciting to imagine that you're standing on a volcano.