Biebrza National Park

Stand still for a moment and listen. Out here, the loudest sound is often the wind moving through sedge — a dry, steady hiss that rolls across the marsh like surf on a distant shore. Underfoot, the ground feels soft, even when it looks firm. The air smells of wet grass, peat and cold water. Above you, the sky is huge and flat, with almost nothing to break the horizon except a line of birch or a single crooked willow.

This is Biebrza National Park, in the far north-east of Poland, in the Podlaskie region. It is the largest national park in the country, and it was created in 1993 to protect one thing above all: water. Specifically, the vast valley of the Biebrza River and the wetlands that spread out on either side of it. Many visitors expect a forest park. What they find instead is mostly open marsh, reed, wet meadow and peat bog.

The river itself is slow and winding. It loops back on itself again and again, leaving behind old curves of water called oxbow lakes, which are cut-off bends of the river. The Biebrza eventually flows into the Narew River further south. Along its course, the valley is usually described in three parts — an upper, a middle and a lower basin. Each one has a slightly different character, from narrow and wooded to wide and almost endlessly open.

Here is the first thing most people miss. The real heart of this landscape is not the river at all. It is the peat beneath your feet. Peat forms when plants die in waterlogged ground and never fully rot away. Over thousands of years, those layers build up slowly, like pages in a closed book. This valley holds one of the largest and least damaged peatland systems in Central Europe. And that peat stores a great deal of carbon, which is one reason scientists care so much about keeping it wet.

In much of Europe, wetlands like this were drained long ago for farming. Rivers were straightened, ditches were dug, and the marshes became fields. Here, large areas escaped that fate. Some drainage did happen, and you can still find old canals and ditches in parts of the valley. But the core of the marsh stayed wild. Because of this, the park is listed under the Ramsar Convention, an international treaty for protecting important wetlands.

Every spring, the valley changes completely. As snow melts across the region, the river rises and spills over its banks. Meadows disappear under shallow water that can stretch for kilometres. Roads become causeways. Trees seem to stand in a lake. This seasonal flood is not a problem for the ecosystem — it is the engine of it. It feeds the meadows, refreshes the peat and creates the conditions that make this place so important for birds.

And the birds are why many people come. In April and May, the marsh fills with sound. One of the most famous sights is the ruff, a wading bird. In spring, the males grow strange, colourful feathered collars and gather on open ground to display. They puff out their neck feathers, jump, bow and spar with each other while the females watch. Birdwatchers travel from across Europe to see it.

The second surprise is a small brown bird you will probably never notice. The aquatic warbler is one of the rarest songbirds in Europe, and it is considered globally threatened. It needs exactly this kind of habitat — wide, wet, sedge-covered fen that is not too dry and not too overgrown. This valley is one of its most important breeding areas anywhere in the world. That quiet, scratchy song from the sedge could be one of them.

Then there is the elk, known in North America as the moose. Biebrza is often described as the best place in Poland to see one. These are enormous animals, tall at the shoulder, with long legs built for wading through deep, soft ground. Early morning and dusk are the best times to look. Scan the edges where open marsh meets birch and willow scrub. Beavers live here too, and wolves are present, though very few visitors ever see one.

In the middle part of the valley lies an area called the Red Bog. It is one of the strictest protected zones in the park, set aside largely as a refuge for elk. The public cannot wander freely inside it. That might feel frustrating, but it explains something important about Biebrza. This is not a park designed around people. It is designed around the marsh, and people are welcome to watch from the edges.

Human history runs through the valley as well. At Osowiec, near the park headquarters, stand the remains of a fortress built by the Russian Empire in the nineteenth century, when this area lay on the empire's western frontier. The marsh made a natural defensive barrier. During the First World War, the fortress was besieged by German forces. One dramatic episode from 1915 involved a gas attack, and the story of the defenders' counter-attack is now told and retold with a good deal of legend around it.

Linked to that era is a long, straight road through the marsh known as the Tsar's Road. It was built by the Russian authorities in the nineteenth century, mainly for military purposes, crossing wet ground that would otherwise be impassable. Today it is one of the easiest ways to see the landscape. As you drive or cycle along it, watch the ditches and open meadows on either side. Herons, cranes and birds of prey often hunt there.

For most visitors, the best way into the marsh is on foot, along wooden boardwalks laid over the wet ground. Some lead out to observation towers, which lift you just high enough to see how far the flat green world really goes. Others lead into stands of birch and alder where the light turns soft and green. Bring insect repellent in summer. The mosquitoes here take their job very seriously.

Before you leave, stop again and look out at the horizon. Notice how little has been built here. No towers in the distance. No road noise. Just sedge, sky and slow water. Perhaps a crane is calling somewhere far off, a rolling, trumpeting sound. The ground beneath you has been growing, very slowly, for thousands of years. As you walk back, step softly — you are walking on one of Europe's quietest archives of time.