Zanskar is a remote valley in northern India, wedged between Ladakh and Kashmir, through which runs the Indus river tributary of the same name. In winter, the numerous villages in the valley would be totally isolated from the rest of the world, if it wasn't for the river, which, freezing over in the coldest months, permits the inhabitants to walk on it. It's a fascinating journey which winds amongst seventy kilometres of gorges, where, at night, one has to shelter from temperatures of -30° inside caves created by the erosion of the soft sandstone. The inhabitants of Zanskar still use the frozen river to transport butter, which is particularly fragrant and appreciated, to Leh market (the capital of Ladakh)