Una, Unac and Krka as three jewels of the natural heritage of the Una National Park, make a combination of valuable natural features, of diverse and preserved natural landscapes of exceptional beauty and rich cultural and historical heritage.
River Una as the greatest natural value, after which the National Park got its name, rises in the village Donja Suvaja below the mountain Stražbenica in Croatia. This is a typical karst spring of upward type, of special green-blue color. In the upstream, from the source to Bihać, the overall fall is nearly 3 meters per kilometer. In this section, Una has features of a real mountain river and its travertine waterfalls, cascades and falls are a true jewel of beauty of which are: a big waterfall in Martin Brod, Štrbački buk, Troslap, Dvoslap and Ripač fall. Down at the waterfalls of Martin Brod and Štrbački buk the water crashes over several small and large falls and waterfalls building a unique travertine formations characteristic of this beauty. The living world in Una, which itself contributes to the creation of travertine formation is particularly interesting. With its structure, mosses - bryophytes are suitable for retention of precipitated calcite, that way making an indispensable link in the creation and growth of travertine formation.
River Unac, rises as mlinski potok ( Mill creek ), under the mountain Šator at altitude of 876 m, flows through the gorge Pojila, four basins and three further gorges. On its course through the National Park until Martin Brod it flows its narrowest gorge, about 350 m deep. The total flow is about 66 kilometers, and has an altitude difference of about 450 m. Unac is the first major tributary of Una that with its exceptional purity and coldness refines Una, and also additionally cools. With its course, Unac fills with water from a dozen different tributaries and springs. In summer, it sometimes dries up in one part, due to the reduced inflow of water from the surrounding forest streams, leaving behind a small lake with hot water and full of fish. On this part, Unac flows like underground, last time rising out from the Black spring about 3 kilometers before the mouth of the Una.
Rivulet (small river) Krka, 5 km long, as the border river with Croatia, throughout its course runs through the National Park, and rises at the foot of the plateau on which the village Cvjetnić lies. Very interesting to the eye, the access to the source is very demanding, so it gives the possibility of full-day excursion that includes a walk in the woods, through naked hilly mountainous regions and getting down to the valley where there is a source with an old mill building.
Parts of the river Una and Unac do make one of the largest fly fishing grounds in Europe, and Una itself is a paradise for lovers of fishing, using dry flies with a water ball and spinning.