February the 2nd, 2026 – The River Una is a Croatian river with one of the deepest sources on Earth. It’s also widely considered one of the cleanest and most pure waterways in all of Europe.
As Putni kofer/Martina Hrupic writes, the River Una is a beautiful 200-kilometre-long waterway close to the hearts of people in both Croatia and in neighbouring Bosnia and Herzegovina. However, this river is not only famous for its beauty. It’s incredibly clean, and its source is quite special: it is the deepest karst river source in Croatia and one of the five deepest in the whole world.
the una – the only one
At 212 kilometres long, the River Una a unique waterway. Not everyone praises only the beauty of its banks, the turquoise colour of its pure water and the excitement of its multiple rapids. It is one of the few rivers in Europe that is so clean that, in its upper reaches, its water is completely drinkable from the source, and its name itself is a testament to its uniqueness. The Romans gave it the name it still bears today, which means one, that is, the only one.
The Una cares little about borders, and one of the first associations when the name of this river comes up is usually not Croatia, but Bosnia and Herzegovina, where it is protected by the national park that bears its name. Despite that, the Una, with one of the deepest sources on Earth, actually originates in Croatia. In Croatia, where about half of its 212 kilometres of this river flows, its mouth is also located. Its waters actually become part of the Sava not far from the settlement of Jasenovac.
The Una River seems unable to decide which country it wants to flow through. It crosses the border between Croatia and Bosnia and Herzegovina on several occasions, and also acts as a border river. The first 20 kilometres of its course are border lands, and then near Melinovac it “opts for” Bosnia and Herzegovina. The border is then found again in Croatia, more specifically in Sisak-Moslavina County.
the una actually “comes from” zadar
The Una actually originates in Zadar County. Its hydrographic system consists of three sources: the main source near the settlement of Donja Suvaja and two smaller ones, Velika and Mala Nateka. These three sources form the Una, which then receives its water from Srebrenica and three smaller tributaries before flowing further north.
The source of the Una River, although karst, is special in several ways. It is located at an altitude of 448 metres, below the slopes of Plješivica and Stražbenica, in a very narrow canyon of daunting cliffs. There, the river is born in the form of a calm and round lake, while also being fed by springs on the bottom and the sides of its bed. It begins being adorned with waterfalls almost immediately. The greatest magic of its source is this: it is the deepest karst spring in Croatia, and it is also among the five deepest karst river sources in the entire world. Previous research has reached a depth of 248 metres, but the bottom has not yet been reached.
a river adorned with protection from all sides
The Una is a river that is rightly subject to numerous protections. Across the border in Bosnia and Herzegovina, it is protected by the borders of the national park, while in Croatia, the source of the Una river with a canyon 150 metres long is protected by the designation of a hydrological nature monument spanning an area of 263 hectares. It was declared as such back in 1968, while the national park in Bosnia and Herzegovina was established only in 2008.
The Una is a Croatian river known not only for having one of the deepest sources on Earth, but also for the very rich biodiversity associated with it. It is home to 30 species of fish, and 11 protected species of plants grow at the source of the Una alone. 170 medicinal plant species also associate their existence with its banks.
