A clear fresh-water lake, in S. of Siberia, 397 m. long and from 13 to 54 wide, in some parts 4500 ft. deep, and at its surface 1560 ft. above the sea-level, the third largest in Asia; on which sledges ply for six or eight months in winter, and steamboats in summer; it abounds in fish, especially sturgeon and salmon; it contains several islands, the largest Olkhin, 32 m. by 10 m.