See a real ‘house of dragons’ in this Slovenian cave

This cavern’s blind aquatic salamanders inspire legends and conservation efforts.

By Rebecca Toy
Published 26 Oct 2022, 11:07 BST
Postojna Cave in Slovenia is one of the biggest tourist attractions in the small country.
Photograph by Zeljko Stevanic, Xinhua, eyevine, Redux

Television viewers have gotten familiar with fictional dragons over the last decade via Game of Thrones and its prequel, House of the Dragon, which just finished its first season. But the long-tailed creatures are real beneath the limestone hills of Postojna, Slovenia. Here, underground caves threaded with rivers reveal wonders of resilient life. Among the crickets, millipedes, and beetles, baby dragons rule what’s considered the most biologically diverse cave in the world.

These almost translucent aquatic salamanders, officially known as olms (Proteus anguinus), have adaptive features that are nothing short of legendary—even without wings and fire. Top predators in their underground world, the amphibians can grow as long as 12 inches, regenerate limbs, live up to a hundred years, and go up to a dozen years without eating. Scientists study their extensive DNA code for answers to the process of regeneration and adaptation.

The olm, a sightless salamander found in caves in Slovenia, Italy, and Albania, can live to be a hundred years old.
Photograph by Nature Picture Library, Alamy Stock Photo

“This is the closest thing to a dragon that I’m ever going to get,” says Postojna biologist Katarina Kanduč.

For centuries these eyeless olms were considered the offspring of hidden dragons in Slovenia. Even now they remain mysterious, classified as vulnerable by the International Union for Conservation of Nature (IUCN) due to a lack of data. Scientists even struggle with determining how many reliably live in their tiny territory of the Dinaric karst that stretches along the Adriatic coast from northern Italy to Albania.

What is certain: Their watery habitat is threatened by chemical contaminants, particularly fertilisers, which pass through the highly permeable rock and are absorbed by these long-living legends. One of the best places to learn about them—and help in their conservation—is Postojna Cave Park, Europe’s most visited tourist cave.

More than 40 million people a year pass through the cave, located less than an hour from the capital city of Ljubljana. Most visitors go on a 90-minute tour past brilliantly white stalagmites and through caverns lit with Murano glass chandeliers before glimpsing the olms and learning about conservation efforts. 

But those wanting to escape the crowds to see baby dragons in their natural habitat can join a limited, non-invasive, lamplit adventure tour deep into the caverns. Part caving adventure, part history lesson, and part escape room, the three-hour experience also includes rappelling, boating, and spelunking activities on the way to the olms’ habitat. 

Slovenia’s pride in its caving heritage and its enduring fascination with mythological beasts fuel this conservation effort—and it’s paying off. Postojna recently announced that 30 baby olms were born in the cave’s research complex, a record-breaking survival rate.

Dragons in Slovenia 

Dragons have long fuelled legends and literature, but Slovenia takes its love affair to a new level. The fearsome-snouted creatures are everywhere, roaring on an iconic bridge in Ljubljana, covering drain covers, and starring in street art murals. The adoration makes sense in the world’s namesake geological karst region, full of sinkholes, caves, and dark depths where, for centuries, residents believed dragons dwelled.

In the past, Postojna residents thought that the warm mist spewing from the cave in the winter was a giant creature’s breath. (It’s actually a result of the cave’s stable internal temperature.) When the cave’s river flooded and ejected strange drowned salamanders, people saw these baby dragons as proof that a much larger parent lurked inside.

“Caves were portals to some other world, dangerous and dark,” says Postojna guide Kevin Klun Valenčič. “You had to meet your fear underground and fight with that, like slaying a dragon.”

Caving for dragons

By lamplight, the foot-long baby dragon has an almost neon shine as it swims in the clear underground river then darts under a rocky outcropping. It was a mighty movement for a normally low-energy creature, one that our small group had hiked, rappelled, and navigated along a strategic path in historic, riverside tunnels to see. According to Valenčič, most people on this tour get at least a glimpse of the cave’s sizeable olm population in the lower river, although there are no guarantees with the elusive animal.

Olm embryos often don’t hatch into salamanders, but Postojna cave has recently been the site of above-average birth rates.
Photograph by Alex Hyde, Nature Picture Library, Alamy Stock Photos
Though olms are sightless, they have highly developed senses of smell and hearing that help them forage for bugs and other prey.
Photograph by Luka Dakskobler, Xinhua, Alamy Stock Photos

In nature, scientists estimate only two in 500 olm eggs hatch. At Postojna at least 30 of 43 eggs have hatched, doubling the rate from 2016 and confirming that the tender care of the Postojna team makes a difference–even when they’re working in the literal and metaphorical dark. “Nobody has done this before,” says Kanduč. “It’s not exactly something you can Google.”

Olms in Postojna’s research area have surprised scientists with eggs for the second time since 2016. 

Their work has earned them a place as a 2022 finalist for the European Union’s prestigious Natura 2000 conservation award

When not in the lab, Valenčič clearly enjoys stepping away from it all and leading tours in the cave—sliding down muddy hills, squatting to find cave shrimp, and taking moments of silence in the complete dark. 

As Primož Gnezda, another scientist on the team, says, “Everyone wants to see a dragon.”

Rebecca Toy is a Kansas City-based writer who covers travel, history, and culture. Find her on Instagram and Twitter.


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