Most of the landmass in Zambia is a high plateau lying between 910 and 1,370 m (3,000–4,500 ft) above sea level. In the northeast, the Muchinga Mountains exceed 1,800 m (5,900 ft) in height. Elevations below 610 m (2,000 ft) are encountered in the valleys of the major river systems. Plateau land in the northeastern and eastern parts of the country is broken by the low-lying Luangwa River, and in the western half by the Kafue River. Both rivers are tributaries of the upper Zambezi, the major waterway of the area. The frequent occurrence of rapids and falls prevents through navigation of the Zambezi.
There are three large natural lakes—Bangweulu, Mweru, and Tanganyika—all in the northern area. Lake Tanganykia is the largest with an area of about 12,770 sq km (32,893 sq mi). Lake Bangweulu and the swamps at its southern end cover about 9,840 sq km (3,799 sq mi) and are drained by the Luapula River. Kariba, one of the world's largest manmade lakes, is on the southern border; it was formed by the impoundment of the Zambezi by the construction of the Kariba Dam.