Lake Khövsgöl holds almost 70 percent of Mongolia's fresh water — a single sheet so clear you can count pebbles several metres down. Pure enough to drink straight from the shore, it is one of only seventeen ancient lakes on Earth, a rift basin more than two million years old that lies just south of the Siberian border. It is often called the younger sister of Lake Baikal, which it feeds through the Egiin Gol and the Selenga a thousand kilometres to the north. Stretching 136 kilometres long and plunging to 262 metres, it sits at 1,645 metres among the snow-veined peaks of the Sayan and Khoridol Saridag ranges, ringed by the larch and cedar of the Siberian taiga. Mongolians call it not a lake but Dalai Eej, 'Mother Sea,' and hold its water sacred; shamanic ovoos, stone cairns hung with blue prayer scarves, mark the shore.
For a few brief months each summer the shore comes alive: wildflowers spread across the meadows, Darkhad and Tsaatan families raise their gers and graze horses and reindeer on the pastures, and visitors take to the water by horseback and open canoe, often sleeping with nomad families. On a windless morning the surface turns to a mirror doubling the forest and sky, and after dark, far from any town, the stars crowd thickly overhead. Since 1992 the lake and its watershed have been a national park larger than Yellowstone — created after decades in which fuel trucks drove across the winter ice from Siberia and dozens broke through, leaking oil into the lake. Most travellers come only for the short warm season, when the shore tracks are passable; by deep winter the entire lake freezes into a road of ice.