Machu PicchuShutterstock / Anton_Ivanov
The INSIDER Summary:

• There are still many secrets about Machu Picchu and the people who built it.
• Much of the city's infrastructure is hidden and there are at least two hidden temples.

Hiking the Incan Trail to the ancient stronghold of Machu Picchu sits at the top of many travelers' wish lists. The sacred citadel—which sits perched high up in the Andes Mountains—was "discovered" (as much as an outsider can discover a local historic site) in 1911 by an Indiana Jones-type Yale professor named Hiram Bingham. He was lead to the ancient city, which was built around the 1450s, by a local boy and was understandably stunned by the beauty and grandeur of the abandoned site.

Bingham shared the existence of Machu Picchu to the modern world in the April 1913 issue of National Geographic and since then the spectacular archaeological site has attracted visitors, researchers, and explorers from around the world determined to unravel the mystery of the site—or simply to bask in its ancient splendor.

Despite the fact that the city is now an UNESCO World Heritage Site and scientists have been studying the sacred mountain retreat for decades, there are still many secrets about Machu Picchu and the people who built it.

Before you head out on your own Peruvian adventure, here are a few secrets of the sacred site. If anything, these make for great hiking buddy banter.

It was never supposed to be discovered.

The Incans were worried (for good reason) that the Spanish would discover and loot Machu Picchu. To prevent that probable ransacking, less than a hundred years after they built the city in 1532, the Incans abandoned it, burning the forest on the way out so the re-growth would hide the trails up the mountain. The plan worked and the Spanish never discovered Machu Picchu and it was hidden to outsiders until Hiram Bingham visited in 1911.

Bingham actually discovered the wrong city.

According to National Geographic, who funded some of Bingham's later explorations, when the explorer was brought to Machu Picchu, he thought he had discovered a different city altogether. Bingham believed that his local guides had led him to the so-called Lost City of the Incas, Vilcabamba, the Inca stronghold where the rulers waged a years-long battle against Spanish conquistadors. It took 50 years of arguing until Bingham was proved wrong, by an explorer named Gene Savoy, who in 1964, proved that the real lost city of the Inca was Espiritu Pampa, west of Machu Picchu.

Bingham thought Machu Picchu was home to a bunch of woman called the 'Virgins of the Sun.'

The explorer may have been good at paying off trail guides, but he had no idea what he discovered. Bingham not only believed that he had discovered Vilcabama, but he also believed that Machu Picchu was the mythical Tampu-tocco, the birthplace of the Inca forefathers. His fallback theory was that Machu Picchu was a sacred convent filled with chosen women known as the ''virgins of the sun,'' and presided over by priests who worshiped the sun god. This delightful theory turned out, sadly, not to be true.

Machu Picchu may have been the original resort town.

According to a group of archaeologists, Machu Picchu was built as a retreat for the royal family. Research conducted by John Rowe, Richard Burger, and Lucy Salazar reveals that Incan ruler Pachacuti Inca Yupanqui, who it is believe built Machu Picchu, may have envisioned the city as a peaceful place to get away from the hustle and bustle of the city in Cuzco. Machu Picchu was basically an ancient hilltop getaway that most likely would have topped T + L's World's Best list in 1457.

There's a good chance it was an incredibly diverse city.

Andean civilization expert Brian Bauer told National Geographic, that there is a great deal of archaeological evidence that the Inca weren't the only people to live at Machu Picchu. While the village didn't have a marketplace, archaeologists have uncovered ceramics from people across the region indicating that people from a variety of backgrounds lived in—or at least passed through—the city.

The Inca were master stonemasons.

The massive structure of Machu Picchu was built without using wheels, iron tools, or even mortar. Instead, according to National Geographic, the rocks were cut to fit together perfectly, using a method called "ashlar masonry." It was a clever move, too. Peru is prone to earthquakes and the lack of mortar has helped the structures remain standing despite the fact that Machu Picchu was built on two fault lines.

Much of the city's infrastructure is hidden.

While the majestic mountain city towers over the surrounding valley, much of the city's architectural wonders are underground. According to Australia's News, as much as 60 percent of the Inca construction is veiled under the terraced hills as part of the network of foundation walls and drainage systems that wind beneath the city.

There are at least two hidden temples.

The Temple of the Moon and the Cave of the Sun are easy to miss. Visiting the Temple of the Moon requires climbing a ladder for an hour up the side of the Huayna Picchu mountain, according to the News. At the top is a small, but stunning temple built into the cliff wall. Intimachay, or the "Cave of the Sun," is tucked below Machu Picchu's main site, which causes many tourists to miss it. The cave was a sacred space, which may have been designed to make the most of the rising sun during the December solstice as part of the Incan wintertime ritual, Capac Raymi.

It may have been part of a pilgrimage route.

While early explorers thought that Machu Picchu was a secluded citadel, modern archaeologists believe that the site was part of an ancient pilgrimage route. Unfortunately, due to the arrival of the Spanish, the pilgrimage trail was never finished, according to National Geographic. While the reasons for the route are lost to the past, archaeo-astronomer Giulio Magli believes the journey to Machu Picchu may have been related to the first Incas who traveled from Lake Titicaca.

There are still archeological discoveries being made at Machu Picchu.

In 2014, French explorer Thierry Jamin found a previously undiscovered door at Machu Picchu, which he believes holds the royal burial chamber of Pachacuti Inca Yupanqui, the Inca ruler that built Machu Picchu. The Peruvian government, though, won't let him open the chamber as it could cause irreparable damage to the site (also, perhaps, they've seen The Mummy).