Postojna Cave is the most famous attraction in Slovenia. Easy reachable by sight viewing road with only 90 minutes drive. Witness a fantastic web of caves, passages and galleries of this unique Karst phenomena. Inside the park you can also visit the Predjama Castle perched in a vertical cliff.
Note: Passport required
Photo By Leandro Neumann Ciuffo from Rio de Janeiro, Brazil (Souvenir shop inside the cave Uploaded by Sporti) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons