Most train journeys take passengers through bustling cities, across rolling countryside or over dramatic mountain passes. In Slovenia, however, one of the country’s most remarkable railway experiences travels in an entirely different direction, underground.
The famous Postojna Cave is one of Europe’s most extensive cave systems, stretching for more than 24 kilometres beneath the Karst landscape. Visitors begin their journey aboard a small train that carries them deep into a world of vast chambers, limestone formations and winding passages shaped by nature over millions of years.
As the train moves into darkness, stalactites and stalagmites emerge from the shadows, revealing a landscape that feels almost otherworldly. The experience is less like a sightseeing trip and more like stepping into a hidden planet beneath the earth.
The cave is also home to one of its most unusual residents: the olm, a rare aquatic creature sometimes called the “human fish” due to its pale skin and adaptation to life in total darkness.
Slovenia’s underground world extends far beyond Postojna. More than 13,000 caves have been discovered across the country, most within the vast karst system, with others located in different regions. Among them are remarkable distinctions: Slovenia is home to the most visited tourist cave in Europe, as well as the deepest underground canyon on the continent. These cave systems were also among the first in Slovenia to be inscribed on the UNESCO World Heritage List, highlighting their global importance.
What makes the experience even more extraordinary is that Postojna Cave operates one of the world’s only underground railways designed specifically for visitors, a journey quite literally beneath the surface.
