Protects an unusual stretch of the Narew River that's nicknamed the 'Polish Amazon', where the river splits into dozens of channels that spread out across a 2km-wide valley, forming a constellation of swampy islets in between. Most of the park's 73 sq km is comprised of rivers, feeder streams and bogs, and much of it is inaccessible to visitors, though you can kayak on stretches of the Narew River and some of its tributaries.
There's also a network of paths and gravel roads that encircle the park, which can be hiked or biked. There's a good nature hike at the Kurowo visitor centre.