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As a Peruvian historical sanctuary, Machu Picchu has captured our imaginations since the dawn of its existence. In the mornings, this mystical city is shrouded in mist, but in the afternoon sun, you'll see majestic stone edifices scattered across an emerald landscape.

Surprisingly, Machu Picchu remained hidden for centuries. However, it later emerged as one of the best-preserved sites of the Incan Empire. In 2007, voters chose Machu Picchu as one of the New Seven Wonders of the World. While you might be familiar with the famous city (and its photo-bombing alpacas), there's still much to learn about this mysterious place. Here are 10 things you likely didn't know about Machu Picchu.

Machu Picchu Means "Old Peak"

Machu Picchu on a cloudy day
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The Incan people spoke an enduring ancient language. In their native Quechua, Machu Picchu translated to "Old Peak." We agree it isn't a very exciting name for a world-famous site. However, the ancient city impresses in other ways. In 2018, more than 1.5 million visitors thronged the famous Inca citadel to see such sights as the iconic Temple of the Sun and Intihuatana stone, a beautifully-carved granite edifice. According to "The Guardian," the ancient language of Quechua is still spoken by more than four million Peruvians today.

Part of the Site Is an Ancient Observatory

A famous astronomical observatory at Machu Picchu
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No one really knows why the Incan people built Machu Picchu, but there are numerous theories surrounding its origin. One of the more popular theories is that the city was a retreat for royal and elite Incas.

Historians are convinced, however, that part of the city once functioned as an astronomical observatory. According to "Scientific American," a cave-like stone structure called Intimachay helped the Inca people track the seasons. The structure has windows on all sides to let in sunlight during solstices and equinoxes. This helped the Inca people know when to plant and harvest crops as well as when to hold religious celebrations.

Between 500 and 750 People Lived There at One Time

Inca city of Machu Picchu
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Compared to today's cities, Machu Picchu had a pretty modest population size. The book "Machu Picchu: Unveiling the Mystery of the Incas" estimates that a maximum of 750 people lived in the city at its peak. Most of the population was from the servant class called yanaconas. They worked in the homes of elite Incas. The Spanish were the first to differentiate between yanaconas de españoles (servants of private citizens) and yanaconas del rey (servants who owed allegiance to the Spanish crown).

The Buildings Are Earthquake-Resistant

A man wanderings through the ruins of the ancient Incan city of Machu Picchu
Credit: Russell Johnson/ Shutterstock

The 750 residents inhabited around 150 buildings in the city. Amazingly, these buildings have managed to stay largely intact in earthquake-prone Peru. According to "National Geographic," builders used a very precise method of stone-cutting to create the structures.

The technique is so precise that not even an ATM card can be slid between the stones. By all indications, the workmen of Machu Picchu used no mortar in fashioning the buildings. That's not only a feat of ancient engineering, but also a method of earthquake protection. We know the region is prone to earthquakes. However, the stone structures are seismic-resistant. The stone walls might tremble during an earthquake, but they inevitably settle down after the tremors subside.

Residents Abandoned the City for Unknown Reasons

Doorway at Machu Picchu
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Machu Picchu was only occupied by the Incan people for about a century, according to "History." It appears that the residents simply abandoned the site, packed up, and left. So, why did they leave? Archaeologists have several guesses. The city was abandoned around the same time as the Spanish invasion of the Incan empire in the 1530s. Perhaps, the people fled as a response to it. However, there's little to no evidence to suggest the Spanish ever found Machu Picchu. Historians and archaeologists agree the most likely scenario is that a smallpox epidemic drove residents out of the city.

Spanish Invaders Couldn't Find the Legendary Site

Machu Picchu in the clouds
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The Spanish left no stone unturned during their conquest of the Incan Empire in the 16th century. In fact, the conquistadors reduced cities to rubble during their occupation. According to the "New York Times," Machu Picchu was largely overlooked by the Spanish. There are two good reasons for this. Firstly, archaeological records indicate that residents abandoned the city before the Spanish arrived. Whether that was due to a smallpox epidemic or a strategic retreat is up for debate.

The second reason the Spanish didn't destroy Machu Picchu is more obvious. They just didn't see it. Thanks to its location, Machu Picchu can't be seen from below. Visitors can only reach the city by hiking up a very long, steep trail. The Spanish invaders simply didn't know Machu Picchu was there, so the city was spared colonial occupation for centuries.

Hiram Bingham "Rediscovered" the Site in 1911

People visiting Machu Picchu site
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Machu Picchu remained a secret to the outside world for nearly 400 years. Locals knew of the mysterious city on the hill and a few explorers even visited the site. However, no one else explored the city until Hiram Bingham visited in 1911. "Smithsonian Magazine" reports that although locals knew about the site, it was Bingham who drew the world's attention to it. He recognized Machu Picchu's social and scientific significance. He worked to photograph the site and make the images available to the public.

Only 5,600 People Are Permitted to Visit Each Day

Travelers hiking the Inca Trail to Machu Picchu
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The Peruvian government recognized the impact of mass tourism on the ancient city. In 2017, it implemented some restrictions on the number of visitors allowed at the site each day. Starting in 2020, there are only three official routes to Machu Picchu. On advice from UNESCO, the Peruvian government instituted timed entries to cope with an influx of tourists to the famous site. Every day, there will be 3,000 tickets available for morning entry and 2,600 tickets for afternoon entry.

The Inca Trail Takes Four Days to Hike

Stairway on the Inca Trail
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Many visitors choose to make it to the ancient city by hiking the Inca Trail, a route that crosses through the Andes on roads built by the Incas themselves. The road is long, winding, and mostly uphill. Even the most eager hikers can only manage about six or seven miles each day. On average, hikers take four or five days to complete the trail. "National Geographic" warns would-be hikers that the Peruvian government now requires a permit to access the trail.

Those permits are selling out months in advance. If a five-day hike isn't for you, opt for the one-day option (you'll still need a permit though). For this option, you'll take a train to the 104 km mark on the trail and walk the last three hours there. It's best to either go early in the morning (to avoid the crowds) or stay overnight on the trail. This way, you can arrive at Machu Picchu by sunrise.

Many Tourists Travel in the Buff to Machu Picchu

Ruins of the ancient Inca city of Machu Picchu, Peru
Credit: OGphoto/ iStock

For some reason, Machu Picchu has experienced an increase in visitors touring the site in the buff. According to "CNN," the Peruvian government had to expel American, Canadian, and Australian tourists from the city in three separate incidents in 2014. Apparently, the tourists took photos of themselves "au naturel" to post on various social media platforms. It's now compulsory to have a guide with you when visiting Machu Picchu, which is good news for everyone involved.