Slovenia Caves

I visited the Škocjan caves in 2011. I think they are considered the less touristy option vs. Postojna. You can see the Škocjan caves only by guided tour; you show up and buy a ticket fo the next tour; maybe you can do it in advance. If you have a car, it's quite easy to drive there. (I did.) By public transportation is a bit more complicated I think.

Yes, I think Postojna is a bit easier by public transportation, but Skocjan is also possible--though quite possibly not on Sunday. As far as I know they both require tours, but after you finish the tour at Skocjan, you have at least two options to return to the entrance, one of which involves a good bit of walking (not through a show cave). The lighting level at Skocjan is low enough that I (at 64) couldn't really distinguish differences in the colors of the formations. I imagine that is not an issue for younger folks. Postojna has gone the colored-lights route.

Thank you everyone - I'm just about booked for all the tours I can handle (sadly I should have started to book earlier as the adventure tours are all booked up).