The road out of Almaty, Kazakhstan's largest city, does not stop at the lake; the climb is half the point. Switchbacks lift you out of the warm, low streets, past the GES-1 hydro station and into cold air with snow on the rim. Big Almaty Lake appears at a bend, 2,511 metres up in the Tian Shan, held in a bowl of granite and spruce under peaks of 4,000 metres. The blue-green is glacial meltwater. It runs milky in spring and deepens until September, when the inflow slackens and the lake sits at its coldest and stillest. You do not go in. This is Almaty's drinking water: nobody swims or wades, and a guard keeps the shore clear. The walk among the boulders and low spruce is for the reflections and the smell of the pines. The level is not fixed either: it stands highest in August and lowest in February, a swing of up to twenty metres that bares wide pale bands of shore.
Above the lake the road keeps climbing, with Kyrgyzstan just over the ridge. It passes the domed Tian Shan Astronomical Observatory, on the slope since 1957, and ends at 3,340 metres at a cosmic-ray station the Soviets built in the late 1940s. A high mountain was the only laboratory anyone had then for the particles raining down out of space. It is still working, and about as high as you get here on wheels. The same meltwater that colours the lake has run the city's taps and its turbines since 1948. Where the road gives up, the walking starts. A long day climbs toward Big Almaty Peak at 3,681 metres, through high meadow and snowfield, and the water shrinks behind you until it is a bright coin at the bottom of the bowl. The road is a thread going past it and further up.