Una National Park

Listen first. Before you look at anything, just listen. The sound here never stops. It is a deep, steady roar of white water pouring over stone, softened by moss and wet leaves. The air feels cool on your face, even on a warm day, and it carries a faint green smell of damp earth. You are standing in Martin Brod, a small village on the upper Una, and the river is the reason this place exists.

Una National Park covers a long stretch of this river valley in northwestern Bosnia and Herzegovina, close to the border with Croatia. It was established in 2008, and it is the largest national park in the country. Martin Brod sits near its upper end. The town of Bihać lies further downstream, toward the north. Between them, the Una runs through forest, limestone canyons and small river villages, with some of the clearest water you are likely to see in Europe.

That clarity is the first surprise. Look into a calm pool at the edge of the falls. On a bright day you can often see the riverbed far below, every pebble in focus, as if the water were barely there. The colour changes with the light. It can be glass-green, then turquoise, then a dark emerald where the river deepens under the trees. Photographers come here for exactly this shift.

There is an old story about the river's name. According to one popular tale, a Roman visitor saw the Una and called it simply "Una", meaning "the one" in Latin, because nothing else compared to it. Historians are not sure that this is the true origin of the name. But locals tell the story often and with pride. Standing here, it is easy to understand why the legend survives.

Now look closely at the waterfalls themselves. They are not made of hard rock alone. Much of what you see is travertine, also called tufa. Travertine is a soft, porous stone that forms when water rich in dissolved limestone deposits calcium carbonate onto moss and plants. Layer by layer, over a very long time, the river builds its own cascades. So these falls are still growing.

That is the second surprise, and it changes how you see the place. The barriers that create the falls are partly alive. Mosses and algae on the wet surfaces help the mineral settle out of the water. This is why the travertine is so fragile. A footprint or a broken branch can damage a formation that took centuries to grow. Please stay on the paths and avoid climbing on the mossy ledges.

At Martin Brod, the Una also meets one of its tributaries, the Unac. The two rivers join near the village, and the land between them breaks into many small channels, islands and cascades. Instead of one single drop, you see a network of falls spread across the valley floor. Footbridges and paths let you move between them. Each turn gives you a new view of water spilling over green stone.

The word "brod" in the local language means a ford, a shallow place where people can cross a river. For centuries, this crossing point made the village useful to travellers and traders. Rivers here were also a source of power. Along the channels of the Una, people built small wooden water mills to grind grain. A few traditional mills still stand in the area, with wooden roofs darkened by age and spray.

If you walk away from the water for a while, look for Rmanj Monastery, close to the meeting of the Una and the Unac. It is a Serbian Orthodox monastery with a long and difficult history. It has been damaged and rebuilt more than once over the centuries. Its quiet stone walls stand in strong contrast to the noise of the falls. Visitors are welcome, but modest clothing and a soft voice are expected.

Further downstream, the park holds another famous waterfall, Štrbački buk. The word "buk" means a roaring waterfall. Štrbački buk lies right on the border with Croatia, and it is one of the most visited sights in the park. It is a separate trip from Martin Brod, so plan time for it if you want to see both. Together they show two very different faces of the same river.

The Una valley is also home to rich wildlife. The river is known for trout, grayling and the huchen, a large and rare salmon-like fish sometimes called the Danube salmon. In the forests on the slopes, there are deer, wild boar and many birds of prey. You are more likely to see a dipper, a small dark bird that walks underwater along the riverbed, looking for insects. Watch the rocks near fast water.

People here also live with the river in a lighter way. In summer, rafting and kayaking groups run sections of the Una, and many locals swim in the calm pools. For many years, a traditional river regatta has brought boats and crowds down the Una. Rules on swimming and boating vary from place to place inside the park, so check with park staff before you get into the water.

Before you leave, stand still for one more moment. Feel the mist settle on your arms. Look at the thin curtains of water sliding over the green travertine, building the falls a fraction of a millimetre at a time. As you walk back toward the village, the roar will fade slowly behind you... and for a while the silence will feel strange, until the sound of the river becomes a memory.