Physical geography
Plains in the north and center rise to southern highlands along the border with Uganda and Kenya; the White Nile, flowing north out of the uplands of Central Africa, is the major geographic feature of the country; The Sudd (a name derived from floating vegetation that hinders navigation) is a large swampy area of more than 100,000 sq km fed by the waters of the White Nile that dominates the center of the country.