The Sacred Valley, and the empire built in terraces

The Urubamba River runs through a valley the Inca called sacred for reasons that were as practical as they were religious: fertile, sheltered and lower in altitude than Cusco itself, it became the empire's principal breadbasket, terraced hillside after terraced hillside converted into productive farmland by an engineering effort that, six centuries on, still holds. Machu Picchu, perched at the valley's edge, tends to draw the crowds and the photographs, but it was one citadel among many; the valley floor beneath it was where the empire actually fed itself.

Terracing as technology, not decoration

The stepped terraces that line so much of the Sacred Valley were not built for appearance. Each one served as a level planting bed, backed by a stone retaining wall and filled with graded layers of soil and drainage material that prevented erosion on slopes too steep to farm any other way, while the walls themselves absorbed and released heat, extending the growing season at an altitude where frost is a constant risk. At Moray, a site of concentric circular terraces sunk into a natural depression, the design goes further still: each ring sits at a slightly different depth and therefore a measurably different temperature, evidence, most archaeologists agree, of a deliberate experiment in growing the same crops under a range of microclimates before selecting the best-performing variety for wider planting.

Ollantaytambo, still inhabited after five hundred years

Further along the valley, Ollantaytambo served as both a religious and military centre, its terraced hillside fortress overlooking a town whose narrow stone streets and water channels follow the same Inca-era grid they were laid out on. It is one of the few settlements in the region still continuously inhabited on its original Inca foundations, which gives it a texture most archaeological sites cannot manage: working doorways and courtyards rather than roped-off ruins, a town that happens to be several centuries old rather than a preserved fragment of one.

Salt, harvested the same way for centuries

A short distance from the valley's main towns, the salt pans at Maras, Salineras de Maras, have been worked since long before the Inca arrived, fed by a naturally saline spring channelled into several thousand small terraced pools where the water is left to evaporate under the Andean sun. The technique has changed remarkably little over the centuries, and the pans remain in active use today, worked by local families rather than preserved purely for visitors, a rare case of a genuinely old technology still doing the job it was built for.

Machu Picchu, and why the Spanish never found it

Machu Picchu itself was built around the middle of the fifteenth century, most likely as a royal estate for the Inca emperor Pachacuti, and abandoned within a century, around the time of the Spanish conquest, its exact purpose still debated by historians. Its survival is generally credited to its location, high, remote and largely invisible from the valley floor, which meant it escaped the destruction the Spanish visited on so many of the empire's more accessible sites. It was brought to wider international attention in 1911 by the American explorer Hiram Bingham, guided to the ruins by local farmers who had known of the site for some time, a detail worth remembering whenever the word "discovery" gets attached to a place that was never, in any real sense, lost.

What the empire left besides stone

It is worth remembering that the Inca state which built all of this lasted, in its full imperial form, less than a century, expanding rapidly from Cusco under a handful of emperors before the Spanish conquest brought it to an abrupt end in the 1530s. The terracing, irrigation channels and road network that survive were built and refined within that short window, which makes the scale of the Sacred Valley's engineering rather more remarkable rather than less: not the accumulated work of millennia, but the product of a few generations who evidently understood the land they were farming in considerable detail.

The Andean dry season, roughly May to September, gives the clearest views of both the valley's terraces and Machu Picchu itself, though it is also the region's busiest and most heavily booked stretch of the year, worth planning around well in advance.