Russia is home to the world's deepest lake: Lake Baikal in southern Siberia. Its maximum depth is about 1,642 metres, making it deeper than any other lake on Earth and deeper than many seas.
Baikal is a vast rift lake formed where sections of Earth's crust are slowly pulling apart. It is estimated to be roughly 25 to 30 million years old, making it one of the planet's oldest lakes as well as its deepest. The lake stretches about 636 kilometres and contains approximately 20% of the world's unfrozen surface freshwater.
Its unusual age and isolation have produced exceptional biodiversity. Baikal supports thousands of plant and animal species, many found nowhere else. The Baikal seal, or nerpa, is the world's only exclusively freshwater seal. The lake also freezes in winter, sometimes forming remarkably clear blue ice.
A common mix-up is the Caspian Sea, which is larger by surface area but is generally classified as a lake because it is an enclosed body of water. Lake Tanganyika is the second-deepest lake, but at about 1,470 metres it does not surpass Baikal. UNESCO designated Baikal a World Heritage Site in 1996.