Thanks buddy! Yeah, this is actually quite common with quarries here in Central Europe. When the quarry is mined out, it gets flooded with water (rain water or groundwater) and it gradually becomes a tourist attraction or a place where people go to relax. There is such a quarry in my hometown too and I saw some in Poland as well.
Btw there is no waterfall in the Velka Amerika Quarry, I think what you mean is just a path that connects the edges of the crater with the bottom ;)