They could have followed the valley but they chose the high route to
Machu Picchu, with its gorges and passes and climactic mountain views. True Andean highlanders, the Incas knew and loved the countless natural zones that lay within the folds of their vast domain. Their trail to Machu Picchu traverses a startling variety of microclimates, beginning with an arid cactus zone on the Urubamba valley floor, rising through native Polylepis forest to bleak high-altitude grassland, and ending in mossy cloud forest draped with orchids and bromeliads.
They celebrated the glory of the snow peaks by setting their trail along a ridge that descended from the sacred summit of Salcantay and ended at Machu Picchu. Wherever some astounding view or prominent natural feature captured their imaginations, they built magical stone outposts — intricate ceremonial settlements of carved stone hewn from the white granite of the region. These cling to mountain spurs, perch on narrow ledges or spill down plunging slopes, with water channels threading among the houses, as though planted there, without human intervention, by an extravagant nature.
All this was abandoned around the time of the Spanish conquest, lying buried beneath the forest until Hiram Bingham set out in 1915 to follow up his discovery of Machu Picchu with a search or the Inca highway leading back to Cusco. Lucky explorer that he was, he found what we now call the Inca Trail and all the sites along it except Wiñay Wayna, that was not discovered until 1941, by Paul Fejos. Today we can hike this trail, seeing much of it intact and easy to imagine as it was in Inca times.