Numismatic cover from Postojska Jama

Postojna Cave (Höhle von Postojna) is located in southwestern Slovenia in a karst landscape formed of limestone. Its branching system of passages was created by the Pivka, which enters the subsurface and dissolved the limestone over long periods. Stalactites and other sinter formations, by contrast, form when water containing dissolved limestone leaves mineral deposits in the cavities. The region belongs to the wider area of the Slovenian Karst, whose landscape name became the international designation for corresponding geological formations.

The year 1213 does not mark the discovery of the cave in the actual sense. People knew and entered at least the more accessible areas earlier. The anniversary is instead based on the oldest known visitor inscription in a section of the cave now called “Gang der alten Unterschriften”. Such carved names and years document the use of the cave long before the beginning of organized tourism.

In the 17th century, the Carniolan scholar Johann Weichard von Valvasor described the cave. A decisive step in its further development came in 1818 with the discovery of previously unknown cave chambers by Luka Čeč, who was working as a lamp lighter in preparation for a high-ranking visit. Regular visitor operations began as early as the following year. In the 19th century, paths, lighting and a cave railway were installed. Postojna thus became an extensively developed cave system for tourism at an early stage.

The cave is also a site for research into subterranean habitats. Its fauna includes the olm (Grottenolm), an amphibian of the Dinaric Karst adapted to permanent life in darkness. Other invertebrate cave animals also contributed to making Postojna a research site for speleobiology.

For Slovenia, Postojna combines natural landscape, tourism history and the scientific study of karst phenomena. The surviving inscription provided a clearly datable occasion to commemorate this national natural and cultural heritage on a commemorative coin.