The source of the River Kupa, one of the many unsolved karst riddles, is one of the most abundant, spacious and deepest water springs in Croatia. At 313 metres above sea level, the water has formed a smaller turquoise-green-blue lake which is 200 metres long and on average 30 metres wide. The water that flows out from here is the full width of the river.
This impressive hydro-geomorphological phenomenon, located 313 metres above sea level, with its tranquillity and rather unusual greenish-blue colour, set in a deep gorge surrounded by forests and high rocks, offers a truly memorable experience. The source is located beneath the western slopes of Mount Risnjak and can be reached from the village of Razloge or from the village of Hrvatsko in the Kupa Valley.