400 miles long, 50 miles wide and one mile deep, Lake Baikal contains one fifth of the planet’s fresh water, as much as all five Great Lakes combined. Because of its depth it does not freeze over until January, and in December vapor comes off the surface and the spray from the waves turns to ice. It contains over a thousand endemic species of animals, including the world’s only freshwater seal (a fat, almost spherical creature) and the delicious, salmon-like omul, which is smoked and sold everywhere near the lake, including on the trains. In stark contrast to the rest of Russia’s waterways, the lake is quite pristine and free of pollution, except for some discharge from a paper mill at the southern end.