Hranice Abyss

The Hranice Abyss, the English name adopted by the local tourist authorities, is the deepest flooded pit cave in the world. It is a karst sinkhole located near the town of Hranice. The greatest confirmed depth is 473 m, which makes it the deepest known underwater cave in the world. Moreover, the expected depth is 800–1200 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.