Graffiti inside the cave dates back to 1213, but Postojna became a tourist attraction in the early 19th century, after new passages were discovered in 1818. Electric lighting was installed in 1884, and rails for a cave train were laid as early as 1872. Today about 5 kilometres of the system are open to the public, revealing halls filled with stalactites, stalagmites and delicate curtain-like formations.
Tours begin with a ride on the underground train deep into the cave, followed by a guided walk through spectacular chambers. One highlight is a glimpse of the olm, or proteus, a blind, pale amphibian that lives only in the caves of the Dinaric karst. The temperature inside stays cool all year, so a warm layer is a good idea even in summer. Just 9 kilometres away, Predjama Castle is dramatically built into the mouth of a cave in a sheer cliff face.
Together, Postojna Cave and Predjama Castle make a memorable day trip from Ljubljana or the Slovenian coast.
