[citation needed] The source of the Una river is located near the Croatian village of Donja Suvaja and consists of multiple smaller springs.

Due to their unique aesthetic, ecological, geomorphological and hydrological value, the spring and the surrounding region, totaling an area of 163 ha (400 acres), were declared a natural monument in 1968.

After emerging from its source, the river flows for about 5 km before reaching its confluence with the Krka river, after which it forms the border between Bosnia and Croatia for about 7 km and then enters Bosnia completely for the first time, flowing through the village of Martin Brod where it forms a cascade of waterfalls with the total drop being about 54 m (177 ft).

After 9 km the river bends west at the town of Kulen Vakuf where it is joined by the small tributary Ostrovica before continuing to flow in a general northward direction.

Downstream of Kulen Vakuf, the river meanders through a valley by the village of Klisa before again meeting the Croatian border after about 8 km.

After entering Bosnia completely for the second time, the rivers forms the Troslap and Dvoslap waterfalls, after which it exits the national park and flows through the villages of Lohovo and Račić.

After that, the river slowly enters the Bihać field, flowing through the villages of Ripač, Golubić and Pritoka, taking in the waters of the Dobrenica and forming multiple river islands and small waterfalls, before finally entering the city of Bihać after about 70 km of total flow.

In Bihać, the river forms multiple islands of varying sizes, often surrounded by small waterfalls, some of which are private property while others are public and often popular bathing sites.

The deposition of carbonate minerals and the formation of porous limestone rock (tufa) and pronounced karst influence is characteristic for this section.

[2] The middle section of the river spans from the city of Bihać to the town of Novi Grad and its confluence with the Sana.

After flowing for about 27 km through it, the river exits the canyon and enters the town of Bosanska Krupa where it takes a turn north.

The total length of the river between Novi Grad and Jasenovac is around 72 km (45 mi), with a gradient of 0.041% and drop of 29.6 m (97 ft).

Its source is located in Republika Srpska, after which it crosses the entity line and enters the Una - Sana Canton where it flows through Ključ and Sanski Most.

After exiting Sanski Most, it crosses the entity line again and takes a sharp left turn at the foot of the Kozara mountain, after which it enters Prijedor and continues to flows towards its confluence with the Una in Novi Grad.

The river is 66 km long and, throughout its course, flows through multiple gorges and canyons, the deepest one lying between Crno vrelo and Bereka in the National Park itself.

Throughout its course there is pronounced karst influence, and the river is partially disappears as a losing stream in part of its course, only to reappear at Crno vrelo, a couple of kilometers before its mouth.

[9][10] There are multiple measuring stations in Bosnia and Herzegovina on the Unac, and their data is show in the table below:[2] The Klokot is a short river with watershed area of about 94 km2 and a length of 4,5 km.

The old defensive moat of the city was deepened, widened and repurposed as an intake channel for the power plant, utilizing the natural drop of the river.

Notable areas include the upper section of the river, with the Una National Park and its waterfalls, the cities of Bihać and Bosanska Krupa and the surrounding countryside.

The tourism sector experiences steady growth, and the number of visitors to the national park has increased every year since its founding in 2008.

[14][15] Rafting is one of the most popular form of outdoor recreation in Bosnia and Herzegovina, and is important part of the national park offer for the river Una.

An abundant ichthyofauna, rich in salmonid species, primarily grayling and brown trout, with the Una being also famous huchen destinations.

[16][17][18] Fly fishing and other angling methods are allowed only in certain sections and under strict rules and regulations of the national park services.

The Una National Park is almost completely located in the Bihać municipality, along with some of the largest waterfalls, canyons, cascades and tourist attractions.

Some of the settlements on the Una river in the Bihać municipality are Martin Brod, Kulen Vakuf, Lohovo, Ripač, Pritoka, Golubić and Ostrožac na Uni.

[20] The river enters the town from the west, just after having exited its large canyon, and continues to flow through the city, turning north.

Completely destroyed trash cans, park benches and vandalized bridges are not an uncommon sight, especially in more obscure, badly lit parts of the cities.

[23] Another large but often overlooked issue is the fact that there are multiple illegal landfills located in the watershed of the river, most notable in the Una-Sana canton.

To this date, there have been no solutions to the problem as the government of the Una-Sana canton is unable to properly organize and find a suitable location for a canton-level landfill.

All of those proposals were met with fierce resistance from the local and international communities for fear of the destruction of the river's unique environment and, eventually, were cancelled.