Grey Glacier is the great ice of Torres del Paine, in the Magallanes region of Chilean Patagonia, ending in a wall of blue ice six kilometres wide and thirty metres tall that stands in a grey lake full of icebergs, and it is sailed among by boat and crossed on foot in crampons. The glacier pours off the Southern Patagonian Ice Field, and it is not even the biggest glacier on that sheet; nearly fifty others come off the same ice. The lake is Lago Grey, silt-clouded and the colour of its name, and the catamaran from the shore weaves between icebergs that have drifted down from the front, to hold position off the wall where the ice breaks with a crack and drops into the water. The blue is not a reflection of the sky: it comes from ice so old and so compressed that almost no air is left inside it, so the ice absorbs every colour except blue. In March 2019 two slabs of about six hectares each broke off the front within two weeks.
The other way to the ice is on foot. Grey is the western arm of the W trek, Patagonia's best-known walk, and the trail climbs from Refugio Paine Grande through lenga forest, past the scarlet flowers of the notro in spring, to the Mirador Grey lookout, where the glacier, the drifting bergs and the Paine peaks line up in one sweep; further on, suspension bridges hang over gorges above the ice with the wind coming off it. From the refuge at the glacier's edge, a short zodiac ride past Nunatak island puts you at the ice itself, and with crampons, helmet and harness you follow a guide onto the surface, among crevasses, meltwater channels and pools of a blue that looks poured. In April the lenga forests around the lake turn red, orange and gold, the short, brilliant Patagonian autumn, as the trekking season ends. Grey Glacier is the ice at the end of the W, and standing on it is the point of the walk.