Known as the "Pearl of Siberia," Lake Baikal is the oldest and deepest lake on earth. Home to more than one thousand endemic species of aquatic life. Located in south central Siberia, Baikal is 636 km (395.2 miles) long, 80 km (49.71 miles) wide, and 1,637 meters (5,371 feet) deep. A watershed of 55,000 hectares (212.4 square miles) feeds the lake through more than three hundred rivers. Only the Angara River drains Baikal. The lake probably began to form about 25 million years ago, at the site of a tectonic rift. The fault continues to widen and there are thermal vents in the lake's depths.