Comment by m4rtink

This is quite normal thing to do for many open pit mines or rather hard not to do if the pit goes below the water table.

There are some very nice natural swimming pools in the local area thanks to that, for example:

https://www.kudyznudy.cz/aktivity/koupaliste-u-libuse-v-lule... (stone quarry, IMHO one of the best summer swimming pools anywhere)

https://cs.wikipedia.org/wiki/Zatopen%C3%BD_lom_v_Blansku (stone quarry)

https://www.jednoustopouceskem.cz/listing/lom-kaolinka-prime... (kaolin mine)