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Machu Picchu's Engineering Marvels

Mountain archaeologist and National Geographic Explorer-in-Residence Johan Reinhard sends word of the new NOVA-National Geographic special Ghosts of Machu Picchu, which premieres tonight on PBS at 8 p.m.

The Incas who built Machu Picchu atop a high ridge in the Peruvian Andes some 500 years ago had no wheels, no iron or steel, no written language. Yet the exquisite estate they created for warrior-emperor Pachacuti endures.

Yale historian Hiram Bingham first described and conducted archaeological investigations of the site with National Geographic research grants during the early years of the 20th century, and Machu Picchu was immediately recognized as an architectural masterpiece. Only recently have scholars begun to recognize and appreciate the extraordinary engineering feats that made Machu Picchu possible, and that have protected it through the years from the region’s heavy rains, mudslides, and earthquakes.

Hydrologist and civil engineer Ken Wright has studied Machu Picchu for 15 years. When he first visited in 1994, he explains in an interview with National Geographic Television senior executive producer John Bredar, he was “blown away … awed by the site, just like every other tourist.” But as he began to look more closely at the canal constructed by Inca architects to distribute water throughout the complex, Wright “realized that this was an engineering marvel.”

The builders invested about as much effort into creating a stable subsurface foundation for Machu Picchu—underpinned by layers of topsoil, sandy gravel, and granite waste rock—as on the visible buildings at the site, Wright contends. More than 700 terraces retained and channeled moisture and preserved soil, helping forestall erosion while providing space for agriculture. The orientation of buildings and the placement of windows within them were carefully planned to preserve vistas of the surrounding mountains, revered as sacred, and of the Urubamba River 1,600 feet below.

Construction likely spanned about 90 years. Shortly after Machu Picchu’s completion, Spanish conquest of the Inca brought its use as a royal refuge to an end. But the Spanish conquistador’s never found the site.

Discover more of Machu Picchu’s secrets—and more about the people who made this jaw-dropping sanctuary in the clouds—tonight on NOVA, from National Geographic News, and in our Mysteries of the Ancient World website.

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