Kostrzyn – small river, Mazovia Region, tributary of Liwiec River, 44.8km long.The river floats through farm area, mainly meadows, forests and bigger settlements: Bojmie, Oleksin, Stara Sucha. Its source is near Domanice village and estuary to Liwiec near Polkow-Dacbogi village. In the main part of the bridge, Kostrzyn was regulated during war. The river naturally turns from the town to its outlet. Kostrzyn Valley is an area under the bird directive.