If there is one thing you need to do in Slovenia, it is to visit the caves of Postojna and Škocjan. Ok, that’s two. But they are close enough you could do them both in a day, even with public transport (plus a manageable dose of walking). And they are both different, worthy of the hefty ~45 euros entrance fees in total.
The visit to Postojna Cave is like a Disney theme park ride, and feels entirely magical. It begins with a train ride inside the cave – a good 5 min where you are literally transported into another world: deep underground caverns where rich treasures in the form of stalactites and stalagmites abound, with droplets and pools of waters glimmering with life. So precious and priceless are these natural formations (some of which date back hundreds of thousands of years) that an accidental touch could be the finger of death. Shades of white, yellow, red, brown – depending on the mineral content – it’s really difficult to describe the vastness of space that can exist below the surface of the earth. Perhaps trying to picture a 60m-high hill inside one of the caverns will help. And then you wonder, what’s supporting all that ceiling? The audio guide in English greatly enriches the guided walk inside the caves. No photography is permitted sadly but then again photos will fail to capture the grandeur and magnificence of the caves. (Yeah, sour grapes, I know…) The adventure concludes with the train ride back to the entrance, which you don’t want it to ever end. It’s cold inside with temperatures below 10 degree Celsius, so have something warm to wear.
The visit to Škocjan caves has a lot more walking, is a lot less magical, but you feel a lot closer to nature. What is unique is the significant underground river that flows right through the caves. You even get to cross a (concrete) bridge that’s 45m above the murmuring river (“rushing” river would have been a lot more dramatic but likely only during the wetter seasons). It’s not a fairy tale adventure, but more like exploring an earth within the earth. The guided tour wasn’t as spectacular as the Postojna one in terms of stalactite and stalagmite formations, but the unguided route (separate ticket) through a more open-air kind of cave is surreal, breathtaking (pun intended; it was a long route), and feels like a completely different world. Best of all, very few tourists take this added option and the tranquil, undisturbed surroundings, makes you feel so small, yet so one with nature. I say again, be prepared for lots of walking.
I will rate Postojna Caves higher as a tourist attraction, hands down. But the Škocjan Caves are not to be missed as well, especially the unguided route where you are left alone to take it all in at your own pace. Both caves are still in the midst of being explored, and who knows? Maybe one day one of them will really lead us to the centre of the earth!