| Unica | |
| Source1 Coordinates: | 45.8198°N 14.2463°W |
| Mouth Location: | Ljubljanica near Vrhnika |
| Subdivision Type1: | Country |
| Length: | 20km (10miles) |
| Source1 Elevation: | 500m (1,600feet) |
| Mouth Elevation: | 308m (1,010feet) (underground) |
| Discharge1 Avg: | 13m3/s (at the source in Planina Cave), 24m3/s (at the outflow in Vrhnika) |
The Unica is a river in Slovenia. It starts as the underground confluence[1] of the Pivka and the Rak in Planinska jama. This is the largest confluence of underground rivers in Europe. 300m (1,000feet) further, the Unica emerges near Planina. It flows north through the Planina Karst Field (Planinsko Polje) through the municipalities of Postojna, Cerknica, and Logatec, where it returns underground.[2] It then flows for about another 10km (10miles) underground, emerging 142m (466feet) lower[3] at multiple springs near Vrhnika to form the Ljubljanica River.