The Soviet Union's four million inland bodies of water chiefly resulted from extensive glaciation. Most prominently they included the Caspian Sea, the world's largest inland sea, and Lake Baikal, the world's deepest and most capacious freshwater lake. Lake Baikal alone held 85 percent of the freshwater resources of the lakes in the Soviet Union and 20 percent of the world's total. Other water resources included swampland - a sizable portion of territory (10 percent) - and glaciers in the northern areas.