Postojna is one of the world’s longest limestone karst caves, recent explorations bringing its length to 24 kilometers (14.9 miles), with the possibility of it being 31km (19.3 miles) by a yet-to-be-found link to the neighbouring Planinska cave.
The cave is considered a national treasure in Slovenia for its breathtaking world of stalagmites and stalactites in strange shapes and bewildering colors, and sizes. It is also a UNESCO World Heritage site. The formations range from slender, pencil-thin stalks, to towering columns that have taken over 13,000 years to form.
But the real treasures to be found inside the Postojna cave are its animal species, with 99 different species being full-time residents and occasionally, when the populations rise, 150 species.
Meet the “dragon’s offspring”
Of all the creatures to be found in Postojna Cave, the olm, or proteus (Proteus anguinus), a salamander, is the star attraction. It is the only cave-dwelling chordate species found in Europe. Unlike amphibians, the proteus is entirely aquatic. It eats, sleeps, breathes and reproduces underwater.
The proteus, or “human fish” is a strange animal, mainly because of its coloration and appearance. It looks like a pale, anemic human. Actually, it is a neotenic animal, or in other words, an animal that keeps its juvenile features. Or you could say that human fish are babies that have taken on adult functions. Strange, no?
Here is something even stranger. The proteus can live up to 100 years, and when food sources are scarce, can go without food for up to 14 years. The olm has sightless eyes but has extremely good chemo-receptors for picking up organic compounds, and sensory epithelia in its inner ears for picking up sound waves. It does have taste buds. The dragon’s offspring doesn’t eat people, but will dine on small crabs and insects.
So the legend goes, if human fish were to grow up, could they not grow into a dragon? Centuries ago, it was believed by locals that the creatures were baby dragons that were brought up to the surface from the depths of the Earth by heavy rains.
In a manuscript called The Glory of the Duchy of Carniola, published in Nuremberg in 1689, Janez Vajkard Valvasor described the folklore and legend of the olm, while documenting its existence by writing, it was “Barely a span long, akin to a lizard, in short, a worm and vermin of which there are many hereabouts.”
Postojna Cave is home to Vivarium Proteus
The new science of Speleobiology was born in 1831 when the Slender-necked Beetle (Leptodirus hochenwarti) was discovered in the Postojna Cave by a local resident of the area, Luka Čeč. It wasn’t too long before explorers began making further discoveries inside the cave, and soon there was a list of almost 100 species of animals, besides the proteus, including, tiny spiders, the unusual tiny-neck beetle, the cave water louse, grasshoppers, butterflies, water snails, bats, and a number of other creatures.
Inside the cave, about 50 meters from the entrance is the Passage of New Signatures. In this chamber is the Vivarium Proteus. A special place for a special creature, the Vivarium proteus is divided into two sections, one for research, and the other, an exhibition. Of course, the research section is devoted to scientific study and research.
The exhibition hall is a world by itself. Visitors can delve into the science of Speleobiology in a science-friendly way with exhibits featuring karstology, Speleobiology, and special presentations of the cave’s occupants. But the favorite exhibit is dedicated to the olm or human fish.
Postojna Cave is the most visited tourist cave in Europe. In the 188 years the cave has been open to tourism, 35 million people have visited. Today, visitors ride a 3.3-mile long electric train through the caverns, with experienced guides to answer their every question. With a constant temperature ranging from 8 to 10° C, the hour and a half tour is very comfortable.