Postojna Cave

Postojna is a 24.34 km karst system near Postojna in southwestern Slovenia, cut by the Pivka River, and it is second in length in the country only to the Migovec System. What it is first in is showmanship, and it has been for two hundred years.

Graffiti inside is dated 1213, so people were going in long before anyone wrote about it. Johann Weikhard von Valvasor, the pioneer of karst study, described it in the seventeenth century. But the modern cave dates from 1818, when it was being prepared for a visit by Francis I, the first Emperor of Austria, and Luka Čeč, the local man responsible for lighting the lamps, accidentally found a whole new section. Archduke Ferdinand came in 1819, the cave was formally opened to visitors, and Čeč became its first official guide. In the 1850s Adolf Schmidl published the first thorough scientific account of Postojna and the Pivka basin, which became a standard reference in speleology.

Then it started collecting firsts. Cave rails and a tourist train were laid in 1872, pushed at first by the guides themselves and later pulled by a gas locomotive. Electric lighting was installed in 1884, before Ljubljana, the capital of the province the cave sat in, had it.

The train still runs, and it is the reason a visit here feels unlike any other show cave: you ride several kilometres into the mountain before you start walking.

The other inhabitant worth the trip is the olm, the largest cave-dwelling amphibian in the world, endemic to this karst and living its whole life underground. The tour includes an aquarium holding some of them. In January 2016 a female olm at the cave laid over fifty eggs, which is rare enough that it made news worldwide, and twenty two young hatched between the end of May and mid July that year.