Rainbow Mountain, Vinicunca in Quechua, is a ridge above 5,000 metres in the Andes of southern Peru, southeast of Cusco, banded in turquoise, gold, crimson and lavender by the minerals in its rock, and almost nobody had seen it until around 2013, when the ice that had covered it melted away. The colours are chemistry: each band is a different mineral laid down as sediment on a lake floor over millions of years, iron for the reds, copper for the greens, sulphur for the yellows, then tilted skyward when the Andes rose, so the stripes run diagonally up the slope like a tipped layer cake. The trailhead is reached by a road from Cusco that climbs to 4,600 metres, and the walk to the ridge is a few kilometres of switchbacks past alpacas and herders as the air thins, the last stretch slow and deliberate for everyone; from the highest point the whole striped mountain lines up with the glaciers of Ausangate, the snow-star apu and most revered mountain spirit in the southern Andes, standing behind it.
The stripes show sharpest in the dry season, May to September; wet-season cloud and fresh snow can grey them out or hide the ridge entirely. The path crosses the grazing lands of the Quechua communities of Pitumarca and Cusipata, who manage it, charge the entry, and lead llama and alpaca caravans across the heights, and their horses wait on the trail for those who stop. A short extra climb beyond the main viewpoint drops into the Valle Rojo, a fold of rust-coloured hills stained by iron-rich rock where the crowds thin out and the red goes to the horizon. The mountain was nearly lost as soon as it was found: for a time a mining company held rights to the ground beneath it, and the communities fought to keep it as a mountain. Thousands now walk up every day in season. Rainbow Mountain is a ridge that the ice hid for millennia, and it has been famous for a decade.