Machu Picchu: What the Inca Built and Why Nobody Quite Knows

Why Machu Picchu was built where it was is not settled. The most convincing current theory is astronomical: the site is oriented so that specific structures align with the sunrise at the summer and winter solstices and with other celestial events, the Intihuatana stone serving as an astronomical instrument as well as a ritual focus. The Inca developed a sophisticated astronomical calendar and integrated it with their agricultural and religious practices in ways that made the relationship between the sky and the ground a central concern of architecture and planning. A mountain citadel with sightlines to multiple horizons would have served this function well. The royal retreat theory, which posits that Machu Picchu was a private estate for Pachacutec, is supported by the quality of the construction and the proportion of elite residential space to servant quarters. The theories are not mutually exclusive.

Getting there from Cusco is more straightforward than the mystique suggests. The Peru Rail service from Cusco to Aguas Calientes, the town at the foot of the mountain, runs several times daily, the journey taking roughly three and a half hours through the Sacred Valley with views of the Urubamba river and the surrounding peaks. From Aguas Calientes, buses run the switchback road up to the entrance gate in approximately twenty minutes. The ticket limits, which various accounts describe as extremely difficult to obtain, were at the time of our visit available without significant forward planning except on specific anniversary dates. Sunscreen is not optional. I know this because I arrived without enough of it and was reminded repeatedly over the following two days.

Machu Picchu is on UNESCO’s World Heritage critical watch list, which it has occupied since 2012, the organisation citing the volume of tourism and the inadequacy of the management infrastructure to handle it sustainably. The site receives around a million visitors annually, each one arriving on a diesel bus up a road cut into the mountain, being guided along paths that are slowly eroding, viewing structures that are slowly deteriorating under foot traffic and atmospheric exposure. The conservation challenge is straightforward in diagnosis and difficult in resolution: the site needs the income that tourism generates to fund its management, and the level of tourism needed to generate that income is the thing that is damaging the site. This is the standard heritage paradox, appearing in its purest form at one of the most significant archaeological sites in the world. The solutions that have been proposed, limiting visitor numbers more strictly, requiring booking months in advance, routing visitors through different sections on different days, have been implemented partially and inconsistently.

Standing in the agricultural terraces below the main residential complex in the afternoon light, with the Huayna Picchu peak rising behind and the Urubamba far below in the cloud, is one of those experiences that has been photographed so many times and described so many times that it seems like it should have lost its capacity to produce a response. It has not. The setting does something that photography, for all its capabilities, cannot adequately convey: puts a specific human scale next to the scale of the mountain, so that what the Inca built is understood not in isolation but in relation to the landscape it sits inside, which is the relationship the builders intended. They chose this mountain, at this height, at this orientation, and built something there that has outlasted the civilisation that built it by half a millennium. That deserves the response it produces.