The Una River gets its name from the Latin word for 'one' - people long ago thought it was simply one of a kind. And it really does look like nothing else. Minerals dissolved in the water give it a vivid turquoise-green colour that changes shade depending on the season, the sunlight, and how fast the river is flowing.
The park's most spectacular sight is the Štrbački Buk waterfall, where the Una cascades in wide steps over rocky shelves draped in bright green moss. The waterfall is about 24 metres tall and spreads nearly 120 metres across - making it one of the widest waterfalls in Europe. Standing near it, you feel a gentle cool mist on your face even on a hot summer day.
The forests around the river are thick and ancient, filled with oak, beech, and silver fir trees. Otters, brown trout, and rare Huchen fish (a type of giant salmon-like fish sometimes called the 'river tiger') live in the Una's cold, oxygen-rich waters. The forest shelters roe deer, wild boar, and many kinds of owl.
In summer, the park is popular for white-water rafting on the wilder sections of the river, kayaking on the gentler stretches, and swimming in the naturally formed rock pools. In autumn, the surrounding forest turns brilliant shades of orange, red, and gold.