The source of the Nadiža is in Italy. The river makes an almost 12-km loop through Slovenia before returning there. Until it reaches the village of Sedlo, it is hidden in a narrow valley full of rapids and deep pools. From that point onwards, however, it enters a widening gravelly valley and almost disappears in its own deep gravel deposits below the village of Robič.
Its waters are inhabited by all species of trout, grayling, Cottus gobio, as well as large numbers of all the species of Alburnus a. alborell, found in our waters – Adriatic chub, Italian barbel, Leuciscus souffia muticellus, Barbus meridionalis caninus, common minnow as well as Austropotamobius italicus.