One lake holds a fifth of all the fresh liquid water on Earth's surface

Lake Baikal in Siberia is both the world's deepest lake, plunging 1,642 metres, and its oldest, at roughly 25-30 million years old. Because of its immense volume it holds about 20% of the planet's unfrozen fresh surface water, more than all five Great Lakes combined, and its age has let thousands of species found nowhere else on Earth evolve within it.

— UNESCO World Heritage Centre, Lake Baikal — Inscribed as a World Heritage Site, 1996