Machu Picchu is an Inca town balanced on a saddle between two peaks at 2,430 metres, above a hairpin loop of the Urubamba River. There is almost no flat ground: about 200 buildings and their farming terraces are stacked down the ridge in steps, held by walls, with the land falling away on both sides. Behind it stands the blunt green cone of Huayna Picchu; below, the dry Andes drop into humid cloud forest. It was built around 1450 as a royal estate for the emperor Pachacuti and abandoned barely a century later. The Spanish conquistadors who destroyed the empire never found it, which is why the stonework is intact and there is no church on the site.
Come at dawn and the whole valley is packed with cloud. As it lifts, the terraces, the grey stone quarters and Huayna Picchu surface one piece at a time, often with llamas grazing at the cliff edge. Inca astronomy is built into the stonework: carved pillars and cut windows mark the days the sun turns, and the whole site was laid out to read them. The ridge takes close to two metres of rain a year, and roughly three fifths of the Inca labour here went underground, into drains and stone fill you never see. Getting in is tightly managed now. You cannot wander: your route through the ruins is fixed before you arrive, and the circuits run one way. That first sight over the ridge stops everyone, whether you walked four days to earn it or stepped off the morning train.