The Pivka Valley was already named as early as 1300. According to some theories, “Pivka” means a “water-swallowing sinkhole”. On the other hand, Melik, a renowned Slovenian geographer, is of the opinion that, since the flooded plains and lakes are dried by the porous soil, the name is not derived from a sinkhole. This peculiarity has thus given name to an entire region.
The River Pivka slowly flows and meanders through the Pivka Valley, and typically floods when it rains. At the edge of the karst Postojna plain, the River Pivka disappears underneath Sovič and makes its way towards the underwater confluence withthe River Rak inside the Planina Cave. The Pivka again surfaces as the River Unica . The River Pivka’s underwater course has also created the largest Slovenian cave, the Postojna Cave.
Source: RDO Postojnska jama