The Green Karst region in southwestern Slovenia is named for its blend of forests with karst formations and caves. Stopping in this region on our drive from Trieste to Ljubljana,  we visited two towns and landmarks of spelaean note: a castle in Predjama and a cave system in Postojna.

Predjama Castle (Predjamski grad) is the world’s largest cave castle. Occupied since the 13th century with some Medieval fortifications remaining, the main structure still standing today was built during the Renaissance. The castle’s most famous occupant was Erazem Luegar, knight and robber baron. In the late 1400s he defended the castle against a siege for over a year. Unbeknownst to the attackers, he used a secret passageway out the back of the cave that was used to get supplies from a nearby town. The castle was owned privately by a succession of rich Austrian knights and counts until it was nationalized at the end of WWII, and turned into a museum.

Nearby is Postojna Cave (Postojnska jama), the second-longest but most visited cave system in the country. An electric train takes visitors deep inside of the cave, which has a stable microclimate at a constant temperature of 50 °F (10 °C). While the entrance of the cave sheltered humans in prehistoric through Medieval times, the interior of the cave wasn’t explored until 1818.  A year later, Ferdinand I (the future Emperor of Austria and King of Hungary) was the first official visitor, and cave tourism began. The cave was later outfitted with a railway car and electricity. In WWII, Germans occupying Yugoslavia stored fuel in the cave. A team of resistance soldiers managed to detonate the fuel stores, setting off a fire that burned for a week and weakening the German resources. That part of the cave is still coated in soot.

A curious inhabitant of the cave is the olm, or proteus anguinus. This creature is an aquatic, snakelike salamander nicknamed “baby dragon” or “human fish” for its pink, flesh-like skin. The olms can be viewed in aquariums at the end of the cave tour, but photographs are not allowed since the animals are blind and extremely sensitive to light, having adapted to the darkness of the caves.

Drawings of the Proteus from the Iconographia Zoologica in the Special Collections of the University of Amsterdam (1700 – 1880).

GREEN KARST, SLOVENIA

“Postojna Cave – the World-Famous Marvel.” Postojna Cave. Accessed 25 Jun 2017. www.postojnska-jama.eu/en/