Machu Picchu: The Secrets of This Fabled Mountaintop City

At its height in the 15th century, the Inca Empire was the largest civilization ever to exist in the pre-Columbian Americas. An estimated 10 million people lived within its borders stretching from the southern edge of Colombia in the north down the west coast of South America through most of Chile.

Archeologists have uncovered many impressive remnants of a highly developed and politically organized Inca culture nearly erased by the brutal Spanish conquest of the 16th century, but none of them approach the physical majesty and sacred mystique of Machu Picchu.

Located 46 miles (75 kilometers) from the Incan capital Cusco in modern-day Peru, Machu Picchu is an abandoned cloud city nestled high in the Andes Mountains. Since it was "rediscovered" by the American explorer Hiram Bingham in 1911, generations of travelers have marveled at its emerald-green terraced gardens and precision-crafted stonework framed by towering peaks above and the roaring Urubamba River below.

"Machu Picchu is a spectacular site," says Christopher Heaney, assistant professor of Latin American history at Penn State University and author of "Cradle of Gold:The Story of Hiram Bingham, a Real-Life Indiana Jones, and the Search for Machu Picchu." "It embodies so much of what we think about Inca history in terms of architectural splendor and the science of empire building and agriculture. It's also an extremely spiritual site."

Historians believe that Machu Picchu was constructed in the 1450s by the emperor Pachacuti, whose reign was marked by aggressive Incan imperial expansion beyond the valley of Cusco. Pachacuti didn't intend Machu Picchu to become a large settlement, but to serve as a royal retreat and a pilgrimage site for the worship of Inti, the Incan sun god.

A Pilgrim's Route

The 27-mile (43-kilometer) Inca Trail, which modern travelers can still hike from the Sacred Valley to Machu Picchu, was originally designed as a pilgrim route that spiritually prepared the Inca for arrival at Machu Picchu. The twisting trail isn't the most direct route, but its heart-pounding ascents past other important ceremonial sites serve to build suspense for the final reveal — stepping out of the cloud forest to face the fabled mountaintop city.

"Machu Picchu was clearly a place built for the effect of its surroundings and its relationship to the mountains around it," says Heaney. "There are sculpted rocks on the site that echo the landscape and the views behind it. That reflects the Inca's understanding that they were building upon the stone below much more than building something disconnected from the world around it."

Machu Picchu's most famous landmarks are believed to have had both religious and astronomical significance for the Inca. The structure known as the Torreon is a rare example of a rounded building in Incan architecture, its shape a continuation of the curved stone it was built upon.

During the Winter Solstice (which is June in Peru), tourists flock to the Torreon to see the sunrise over the snow-capped Salcantay Mountain, shooting a beam of light through a perfectly aligned window and onto a notched stone. On a clear and starry night in June, that same small window frames the Pleiades constellation, which marks the arrival of a new agricultural year.

The large, smooth-carved stone known as the Intihuatana or "hitching post of the sun," also points directly at the sun during the Winter Solstice, the shortest day of the year.

Johan Reinhard, who studies the "spiritual geography" of the Incan Civilization, told Mark Adams, author of "Turn Right at Machu Picchu," in Adams' book that "Machu Picchu is sort of like the Inca cosmos written on the landscape."

After Pachacuti died in 1471, his mummy likely resided in the cave below the Torreon, but only temporarily. Heaney says that mummies of Inca royalty weren't buried or even considered dead, but had "active social lives." Pachacuti's descendants and servants would have paraded his mummy from city to city so he could "visit" with old friends.

One of the most remarkable achievements of the Incan builders was their masonry. Not only at Machu Picchu, but at other ceremonial sites in Cusco and the Sacred Valley, visitors marvel at thick stones perfectly fitted together without any mortar. Sometimes adjoining stones aren't even the same shapes or sizes, yet they're interlocked like a monumental jigsaw puzzle.

The lack of mortar may help explain why so many of Machu Picchu's walls and stone structures remain intact despite centuries in a highly active earthquake zone. When the ground shakes, the stones are said to "dance" in place and resettle into position when the tremors stop.

Hiram Bingham's Rediscovery

When Hiram Bingham, a history lecturer from Yale University on a mission for the National Geographic Society, was first led into Machu Picchu by the Peruvian farmers living on the site, it was the masonry that clued him into the fact that he had stumbled onto something big.

"The buildings were covered with trees and moss and the growth of centuries, but in the dense shadow, hiding in bamboo thickets and tangled vines, could be seen, here and there, walls of white granite and ashlars [square masonry] most carefully cut and exquisitely fitted together," wrote Bingham in his best-selling book "Lost City of the Incas." He was then shown the Torreon. "Dimly, I began to realize that this wall and its adjoining semicircular temple over the cave were as fine as the finest stonework in the world... It fairly took my breath away."

Historians believe that Machu Picchu was abandoned in the 1550s, but no one knows exactly why. Spanish conquistadors led by Francisco Pizarro had arrived in Peru in 1532 and defeated an Incan army weakened by a recent civil war. The surviving Incan ruling class retreated into the Andes and made a last stand in 1572 at the "lost city" of Vilcabamba. But the Spanish never set foot in Machu Picchu, which doesn't appear in any of their chronicles.

Heaney says that while Machu Picchu was abandoned in the 16th century, it was never truly "lost." Historians have found wills and property records of Inca noblemen and their descendants that refer to "Picchu" as late as the 19th century. Not to mention that Bingham and other Western explorers before him were tipped off by locals about large ruins throughout the Sacred Valley.

But it was Bingham, the self-made swashbuckling explorer, who crossed (crawled across) the Urubamba on a bridge of lashed tree trunks, hiked (mostly crawled) up a steep mountainside on the morning of July 24, 1911 and was introduced to the Richarte family, who planted their crops of tomatoes and peppers in the terraced garden plots of Machu Picchu. The rest is history.

Bingham's stunning photographs of Machu Picchu graced the cover of National Geographic in 1913 and the site became an instant international tourism phenomenon. Even with controls in place to limit the amount of visitors who can walk the Inca Trail and enter the site each day, an estimated 1.5 million people now visit Machu Picchu every year. And the Peruvian government is even thinking about constructing a new airport only miles away.

Heaney, who has spent a lot of time at Peru's historical sites conducting research, is worried.

"That part of the world is absolutely special," he says. "It's sad to think of the place being loved to death."