Situated in south-east Siberia, the 3.15-million-ha Lake Baikal is the oldest (25 million years) and deepest (1,700 m) lake in the world. It contains 20% of the world's total unfrozen freshwater reserve.

Lake Baikal in southern Siberia, Russia, is the deepest lake in the world, reaching a maximum confirmed depth of 1,642 meters (5,387 feet). It is also the world's oldest lake (25–30 million years) and the largest freshwater lake by volume, containing approximately 20-23% of the world's fresh surface water—more than all the North American Great Lakes combined. Baikal sits in a continental rift valley where the Earth's crust is slowly pulling apart; if you were to remove all the water, the rift floor would be nearly 9 kilometers deep. The lake is so massive that it has its own unique ecosystem, home to thousands of species that are found nowhere else on Earth, including the Nerpa, the world's only freshwater seal. In 2026, despite its remote location, it remains a site of immense scientific interest for its water clarity and its role in climate research. For travelers, the lake is famously "crystal clear," with visibility sometimes reaching 40 meters deep. Its status as a UNESCO World Heritage site since 1996 highlights its importance as one of the most significant natural wonders on the planet.