Pfingstsee

Also this lake is owed to the mining. The seams in the subsurface can be thought of slowly and there are always such depressions. It's just good that nature is stronger than humans. Here a little stream meandered a few years ago.

Here you can observe wild ducks, wild geese and other waterfowl along with their offspring.

The Heidhofsee is a lake in the Kirchhellen district of Bottrop and, at 4.8 hectares, the second largest in the city.[1] It was created by mining quartz sand. Since 1973, the Heidhofsee, together with the Heidesee, has formed a local recreation area. The lake offers meadows on its southern bank for tourist use. Parts of the lake are protected biotopes. Heidhofsee and Heidesee are used for fishing.
de.wikipedia.org/wiki/Heidhofsee
The Heidesee in the Kirchheller Heide is an approximately 34 hectare former quarry pond in the Grafenwald district of the Bottrop district of Kirchhellen in North Rhine-Westphalia.
de.wikipedia.org/wiki/Heidesee_(Bottrop)