The Inca emperor Pachacuti had an eye for real estate. That much is clear as our guide unravels the intricate history of his sprawling mountain estate, Machu Picchu, from one of the site’s high stone terraces. But as dawn breaks over the surrounding mountaintops, chasing away the morning mist and illuminating the ruins below, the full grandeur of “The Lost City of The Incas” explodes into view. In an instant, any doubt as to why Pachacuti selected this fantastically inaccessible spot for the seat of his empire, or why modern scholars chose it as one of the New Wonders of the World, evaporates.Perched atop an 8,000-foot-high ridge against a seemingly endless backdrop of ancient peaks and emerald jungle, the sacred site is really more of a small city than a royal refuge, encompassing upwards of 140 stone structures—from towering temples to simple hovels—that cling stolidly to a rocky crag above Peru’s Urubamba Valley. Looking down the precipitous mountainside, it’s also clear why this remote citadel eluded detection by conquistadores, explorers, and adventurers for nearly 500 years until historian Hiram Bingham “rediscovered” it in 1911 (it’s nearly invisible from below).Not that it’s especially easy to appreciate that remoteness today. More than…