It flows through the Suwałki Region of Poland, including the north-western part of the large Augustów Primeval Forest wilderness area.

After an intense campaign of protests in Poland and abroad and also counter-protests of the local community, the plans have been changed, and now the highway has been rerouted to completely avoid the wilderness area.

The Rospuda flows through typical young glacial landforms: postglacial channel lakes, eskers (long, narrow, winding ridges composed of stratified sand and gravel), and flat outwash plains.

In the upper reaches of the river, in the stretches between lakes, the Rospuda has a narrow winding channel of a rocky bed with rapids, for which it slightly resembles a mountain stream.

Sudden bends, rocky shallows, rocks and stilts driven in the bed of the river, or felled trees require attention, reflex, and experience in dealing with such obstacles.

In the lower reaches of the river, on the other hand, monotonous landscape can prove tiresome since the Rospuda winds through reeds blocking out the views.

According to Professor Knut Olaf Falk, the name Dowspuda was rooted in the word Dau-spūda, which, in the extinct western Baltic language - Yotvingian, meant "to push" or "heavy pressure" and stems from the fact that, in the springtime, the river raises its level by about one meter, which results in pumping water back up its tributaries and changing its flow.

Picturesque ruins of the neo-Gothic Pac Palace still stand on the high river banks in Dowspuda village, located to the south of Raczki.

In 1824, Ludwik Michał Pac, the owner of the palace, ordered twelve stone stairs built on the three-kilometer-long segment of the river between Raczki, Dowspuda and below to beautify the area with waterfalls.

The Rospuda Valley is one of the most valuable wetland areas (blanket, raised, and temporary bogs) with natural, intact water relations.

For example, there are 19 kinds of Orchidaceae (all of which are under strict protection), including musk orchid (Herminium monorchis), and white variety of early marsh-orchid (Dactylorhiza majalis).

The Rospuda Valley and its adjacent forests are inhabited by the following protected birds: hazel grouse (Bonasa bonasia), the capercaillie (Tetrao urogallus), spotted crake (Porzana porzana), the corn crake (Crex crex), the common crane (Grus grus), the white-tailed eagle (Haliaeetus albicilla), lesser spotted eagle (Aquila pomarina), marsh harrier, the European honey buzzard (Pernis apivorus), the Tengmalm's owl (Aegolius funereus), the white stork (Ciconia ciconia), the black woodpecker, the white-backed woodpecker (Dendrocopos leucotos), the red-backed shrike (Lanius collurio), the barred warbler (Sylvia nisoria) and other.

For big mammals, like wolves or deer, the Rospuda Valley serves as a migratory corridor, through which they move west from Augustów Primeval Forest and Biebrza National Park.

In December 2006 the European Commission opened legal infringement procedures against the Polish government for consenting to the road developments, which would severely damage important and protected natural sites.