The Orkhon waterfall — Ulaan Tsutgalan to Mongolians — drops off the open steppe with no warning at all. The flat grassland simply cracks into a black basalt gorge, and the river pours into it. About twenty metres high, it is the widest waterfall in the country, and yet for much of the year it is barely there. The falls run only once the first heavy summer rains have filled the river. They thunder through July and August, then thin as the land dries, and in a lean year the drop can slow to a trickle. The rock beneath them was laid down roughly twenty thousand years ago, when lava flows buried this reach of the Orkhon Valley under thick sheets of basalt. The river has been cutting its canyon down through that black stone ever since.
Stand at the rim and the spray drifts up cool against your face. Below the black cliffs a green plunge pool gathers, cold enough to catch your breath. All around lies pure Orkhon Valley country: larch woods, horses and yaks grazing loose, and ovoo stone cairns strung with blue silk scarves that snap in the wind. This valley has been the cradle of one nomadic empire after another, and the ruins of Karakorum, Chinggis Khaan's old capital, lie a few hours north. Reaching the falls still means a long, jolting drive on dirt tracks, and most travellers stay out here in nomad ger camps beneath a sky untouched by light for hundreds of kilometres. Go in winter and you find no waterfall at all, only what is left of one.