Big Almaty Lake changes colour with the seasons — pale green one month, deep turquoise the next, silver on a grey afternoon. That is real physics: glaciers on the slopes above grind rock into a powder fine enough to hang in the meltwater and scatter the blue-green end of the sunlight back at you. It looks like a classic glacier lake, but the basin is tectonic, opened by the earthquakes that shaped most lakes in the Tian Shan. The water sits at 2,511 metres in the Trans-Ili Alatau, the northern wall of that range, only fifteen kilometres south of Almaty. A steep winding road carries you from the warm city to this cold, peak-ringed bowl in about an hour. Three summits close the skyline: the Peak of the Soviets at 4,317 metres, Ozyorny and Turist, all inside Ile-Alatau National Park.
You cannot swim, boat or camp here. The lake is the reservoir that supplies Almaty's tap water, so the shoreline is fenced, a guard keeps it empty, and you look at the water rather than enter it. That restriction is what keeps it quiet. Instead of a crowded beach you get thin, cold air that smells of Tian Shan spruce, the hiss of wind off the ice, and the peaks hanging upside down in the still water. A short steep scramble above the northern dam puts the whole turquoise sheet and its ring of peaks directly beneath you. This is also a border zone — Kyrgyzstan lies just over the ridge — so carry your passport and expect a checkpoint if you climb higher. Above the lake, a domed observatory has watched the sky since 1957, and the road grinds on to a Soviet-era cosmic-ray station at 3,340 metres that still runs. The turquoise burns brightest in autumn.