The Mysterious Inhabitant of the Dark Aquatic Underworld of the Postojna CavesProteus or human fish, a tailed amphibian the colour of human skin and unique to the Slovenian and Dinaric Karst, was discovered in the famous Postojna cave system as the greatest rarity among 190 varieties of animal life. It has gradually became the symbol for the Slovenian subterranean world. The discovery and study of a creature that was initially thought to be a small dragon, gave rise to spelaeobiology, the study of living cave fauna and flora, which had its start in Postojna.
The amphibian is 30 centimeters long, the colour of human skin and reproduces its young with eggs and also as living young. Proteus has adapted to underground life by using only an exceptionally small amount of oxygen. It has atrophied eyes and lungs and breathes through gills like fish.
Initially "človeška ribica" was considered to be the progeny of the dragon. Three hundred years ago Valvasor reported this seriously as a valid point of view.
After serious biologists such as Laurent in 1768 had described Proteus, it took a while before the decision was made how to classify it within the animal world. Even the great Linnaeus thought it was essentially a lizard. The human fish was properly investigated only at the beginning of the 19th century when it was finally confirmed that this was a distinct species of animal.