Postojna Cave, Slovenia's most remarkable natural sight and the most visited show cave in Europe is one of the most beautiful caves, and one of the richest in terms of cave formations or 'speleothems'. In prehistoric times people used the cave as a refuge. Later, the local inhabitants enjoyed showing visitors the cave's entrance passages and chambers, where they would sign their names on the calcite-covered walls and speleothems.

The Republic of Slovenia issued a commemorative coin to mark the 800th anniversary of the first recorded visit to Postojna Cave, depicting a stylised spiral ending in two speleothems. The spiral represents the length and age of the cave, and at the same time indicates the path that has led visitors into the cave for 800 years.