Vinicunca earns its reputation. At over 5,000 meters in the Peruvian Andes, this mountain’s flanks are banded with vivid stripes of coloured sediment — deep reds, ochre yellows, mineral greens and blues — exposed by glacial retreat over thousands of years. The approach is long, the altitude is unforgiving, and the colours are extraordinary. Both things are true at once, and somehow the difficulty makes the arrival more vivid.