Pangong Tso is a salt lake 134 kilometres long in the high desert of Ladakh, in northern India, at about 4,250 metres, and it changes colour through the day from pale turquoise to a deep, almost black blue, with nothing on its shores but bare brown mountains and a few tents. The colour is nearly pure optics: with almost no plankton or silt to cloud it, the shade you see depends on the sun's angle, the depth and the sky it mirrors. The lake has nowhere to drain. It once emptied into the Indus and was cut off long ago, so the salts carried in by mountain streams stay behind, and nothing lives in the water but small crustaceans; the birds that come in summer work the boggy ground where the meltwater streams arrive. Less than half of the lake is in India; the rest stretches east across a contested border into Chinese-held territory, and the line runs through the water.
The road from Leh crosses the Chang La, a pass flanked by glaciers and high enough to leave you short of breath at the tea stall on top, then drops through bare valleys to the shore near Spangmik. Tented camps line the lake there, canvas over a frame and most of them unheated, pushed back from the water since camping on the bank was banned in 2018. The Changpa herders who live here keep ponies at the viewpoints for rides along the water's edge, and behind the beach their animals graze: the big shaggy ones are yaks, and the smaller herds threading between them are changra goats, whose winter undercoat is combed out for pashmina. At night, far from any town, the Milky Way arches over the still water. In winter the lake seals over despite its salt: ice forms from late December, thickens through January, and by late February is firm enough that a marathon is run on it. Pangong Tso became famous from the last scene of a Bollywood film, and the crowds it brought have not changed the colour of the water.