The Kras cave system near the town of Postojna, one of Slovenia' biggest tourist attractions, is among the few locations in southern Europe where this enigmatic animal has been discovered. Its reproduction has so far only been observed in captivity.

The laying of the eggs, which began on 10 August, has been documented, resulting in the first natural environment footage of an olm during reproduction.

According to representatives of the Postojna Caves, the event has caused excitement among experts, as it is unique at the global level.

Since it opened to tourists in 1819, the cave was visited by the 35-millionth visitor last month. Last year it was visited by more than 500,000.