Small train with wooden benches takes you from entrance to the deeper parts of cave, from where you have a walking tour of the caves. Later, he takes you to the exit. Train consists of small "locomotive" with driver, and wagons with two wooden benches, each for two people.
The ride lasts around 15 minutes, and it's denitely worth your time, because you can see large part of the caves. However, water drops from ceiling so be prepeared for that.
And don't rise from your seats during the tour, because you could hit your head in the rocks, because tunnels are pretty narrow.
Our time in Slovenia was short so we opted to rent a car so that we could fit everything in. It took us less than an hour to get to Postojna from Ljubljana, we decided to use the A1 toll road since we knew it would be well marked and we didn't have a real map, just the simple ones in Rough Guide. The toll was 2.10E to Postojna, stay out of the ABC lanes which are for people with prepaid tolls. We headed in the direction of Koper and then turned off when we saw the sign for Postojna Cave (Postojnska Jama), I think attraction signs are brown in color. From the toll road, the route to the caves is very well marked, parking is 2.50E and you pay when you exit.
Postojna lies on the main line between Ljubljana and Koper/Venice and so is easy to reach from either location. I came here from Maribor in the north of the country on a train that went to Venice. The station itself is quite a walk from the town centre and even further from the cave entrance. As you come out of the station there is a map opposite the station entrance
which shows you the route to take to the town centre. It’s best to walk down the hill on a path that takes you back up the other side and then onto a road that leads you into the town centre. The walk takes about 20 minutes to the caves.
The cave railway was built in 1872 which started with guides pushing little carriages along the rails before it was electrified in 1884. The train takes you about 4km into the cave and travels quite quickly. Some areas are quite low so you have to watch out where you’re going if you’re fairly tall. The train brings you into a large area known as the Great Mountain where you get out and follow the crowd to waiting areas which are divided into five different languages such as English, Slovene, and Italian etc so that your guide can narrate to you on the main features of the cave during the tour. The only thing with this is that the English tour is very popular as it’s made up of British, American, Australians etc as well as non-English speaking nations such as the Dutch and Japanese as there isn’t a tour for them in their own language.
Driving by car is probably the best way, as there is some beautiful places around to stop at, but failing that there are plenty of trains and buses running from Ljubljana to the two. The trains run direct from Ljubljana's main station, and take just over an hour. There are even some international trains that pass through the town, and you can get a direct train from Venice, which takes about three hours, or even travel all the way to Budapest.