The open mouth of the Hranická abyss falls through steep rock walls to a depth of 69.5 m to a lake, the bottom of which still remains a mystery. The total confirmed depth, including the dry part, as of 2022 is 519.5 meters (dry part 69.5 m + flooded part 450 m), which makes it the deepest flooded abyss in the world. According to estimates, the abyss could reach a depth of between 800 and 1200 m, as indicated by the temperature and chemical composition of the water in the lake. This is also confirmed by other research published in the professional press in 2020. The abyss was created by the collapse of the cave ceiling, which was eroded by aggressive acidic solutions in the limestone from below to the surface.