After the completion of the Oberkassel/Ramersdorfer basalt quarrying in the 19th century, some of the up to 70 sMeter deep quarrying sites filled with groundwater. Embedded in cliffs, the Dornheckensee …
Deer ponds and elector ponds are part of the villa lakes. The villa lakes are remnants of the opencast mining that was previously operated in the Ville. These remaining holes …