Cavern upon cavern and tunnel upon tunnel run their way deep into the Slovenian underground around the city of Postojna, forming the country’s second largest cave system, and the single deepest, publicly-accessible system on the planet. First discovered in the early 19^th century, this fascinating subterrane is loaded with colossal stalactites and karst rock formations, and affords visitors a remarkable glimpse of geological phenomena in action. History abounds throughout the caverns too, and guests can still ride the old railway lines though the passages, see burn marks from the Second World War and witness graffiti from the before the 19^th century.

Away from the underground system, Postojna tour guides are also at hand to show visitors the mighty Predjama Castle, nestled in its own gaping cave mouth just to the north. And in the town itself there are classic Slovene eateries to enjoy, serving up Hungarian goulash, Slavic dumplings and frothy beer; framed by the quaint red-tiled roofs of the historic buildings all around and the looming peaks of the Dinaric Alps in the distance.