In the first part of its course on the limestone, the Reka still flows on the surface, along an approximately four-kilometre-long gorge that ends with a magnificent wall under which it disappears underground. The Reka River blind valley is the largest in Slovenia. In the distant past, probably in the Early Pleistocene, that is a few hundred thousand years ago, the ceiling of the cave collapsed some 200 metres from the sinks; as a result, the collapse dolines Velika dolina (up to 165 metres deep) and Mala dolina (120 metres) were created, separated by a natural bridge, a remnant of the original cave ceiling. Above the caves, between the wall above the sink and the walls of Mala dolina, lies the village of Škocjan. Close to the houses, there is another entrance to the underground, a ninety-metre-deep abyss called Okroglica, which ends just above the underground Reka River.
At the bottom of Velika dolina, the Reka River finally disappears underground and resurfaces again thirty-four kilometres away at the springs of the Timava River, not far from the Adriatic coast. Part of the Škocjan Caves in which the Reka River flows, namely the Šumeča jama (the Murmuring Cave), is only 3.5 kilometres long, between 10 and 60 metres wide and over 100 metres high underground. The length of all cave passages totals approximately 6 kilometres, while the vertical difference between the highest entrance (Okroglica abyss) and the lowest point in the caves reached by man, that is the siphon, is 205 metres. At some places, the gorge extends into underground chambers. The largest of them, Martel's Chamber, is 308 metres long, 89 metres wide on average (reaching a maximum of 123 metres) and 106 metres high, with the highest point of the ceiling at 146 metres above the Reka River bed (Drole, 1997). The largest cross-section measures 12,000 square metres, thus giving this chamber a volume of 2.2 million cubic metres.
Prepared by: Borut Peric