The Polesian Lowland is a lowland in the southwestern portion of the East European Plain in the drainage basins of several rivers including the Dnieper, Pripyat and Desna. It stretches along the Belarus–Ukraine border. It basically defines the historical region of Polesia. It is politically split into the Belarusian Polesia in the south of Belarus, Ukrainian Polissya in the north of Ukraine (where Волинське, Рівненське, Житомирське, Київське Полісся are distinguished), the eastern part of the lowland extends into Bryansk Oblast in the Russian Federation, and the western part extends into Poland. The lowland has an area of 270000 km2. The Polesian Lowland is characterised by predominance of sandy lowlands with large, mostly swampy valleys. Its average elevation is 150 - 200 m, while its maximum elevation is 316 m (Ovruch Ridge).