The Hranice Abyss (čeština. Hranická propast) is the deepest abyss in the Czech Republic. It is located near the town of Hranice (Přerov District). The lowest confirmed depth (as of 3 October 2012) is 442,5 m (373 m under the water level). In this moment it is the second deepest underwater cave in the world, however the expected depth is 700–800 m
The Hranice Abyss was created by a collapse of the cave roof, which was eaten away by warm carbonic acidulous spring water in limestone.