This is probably the biggest tourist trap in the whole of Slovenia as its right outside the biggest tourist attraction in Slovenia. There are all kinds of tacky stalls and shops that line the road up to the cave entrance that sell everything from photos on plates to tacky T-shirts and such like. Some of the stuff is quite interesting like the minerals and other rock formations but most of it is pure tat.
On top of the cave you can also visit the Speleobiological Station where there is a display of the cave fauna. This was a huge disappointment for me. You barely see anything, so unless you are a huge fan of spiders and insect, you can skip it. You can see the most famous cave creature, the human fish (proteus anguinus) in the main cave, you don't have to come here anyway.
Fun Alternatives: Just settle for the main cave, where there is a display of the main attraction of the cave wildlife, the humab fish (proteus anguinus). Which is not really a fish, but an amphibian.