Rwanda lies on the great East African plateau, with the divide between the water systems of the Nile and Congo rivers passing in a north–south direction through the western part of the country. To the west of the divide, the land drops sharply to Lake Kivu in the Great Rift Valley; to the east, the land falls gradually across the central plateau—its grassy highlands are the core areas of settlement of Rwanda's peoples—to the swamps and lakes on the country's eastern border. Almost all of Rwanda is at least 1,000 m (3,300 ft) above sea level; the central plateau is between 1,500 and 2,000 m (4,950–6,600 ft) high. In the northwest on the border with the DROC are the volcanic Virunga Mountains; the highest peak, Mt. Karisimbi (4,519 m/14,826 ft), is snowcapped. Lake Kivu, 1,460 m (4,790 ft) above sea level, drains into Lake Tanganyika through the sharply descending Ruzizi River. The Kagera River, which forms much of Rwanda's eastern border, flows into Lake Victoria.