Above Yuhu the track climbs through pine woods and meadows grazed by cattle and horses, then drops into Ganheba, the 'dry river flat': a broad valley floored with white limestone gravel and sand. Straight ahead the peaks of Jade Dragon Snow Mountain fill the sky. The massif has a dozen summits above 5,000 m, the highest being Shanzidou at 5,596 m, and 19 glaciers are mapped on it. The surface changes every few minutes, from packed dirt to loose stones to patches of soft white sand. On sand, keep your weight back, keep pedalling gently and go easy on the front brake. Your guide chooses the loop, somewhere between 16 and 25 km, depending on how the group is riding. From October to May the sky is at its clearest and the grass turns gold, as in the photo, with snow lower on the peaks in late winter. In the summer rains the meadows are green but the summits are often hidden. There is little shade on the valley floor and the white ground reflects the sun, so bring sunglasses and sunscreen.