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1. Hi, I'm John Green, welcome to my salon. This is mental_floss on YouTube, and did you know that about 2,500 people visit the lost city of Machu Picchu, Peru every day? It's believed the location was built around 1400 CE for an Incan ruler and probably was deserted around when the Spanish took over. The ruins sit at about 8,000 feet above sea level, and interestingly, its discoverer was looking for a different lost city, Vilcabamba. Anyway, that's the first of many lost cities, most of which have since been found, that I'm going to tell you about in this video today. And speaking of cities and towns and being lost and being found and paper—Paper Towns is a book that I wrote that's now being turned into a movie. It comes out July 24 in the U.S. and other places at other times.

2. In 2015, a group of expeditioners found a lost city in Honduras known as White City or the City of the Monkey God—a place that people had been looking for since the 1920s. Archaeologists then found a bunch of artifacts from between 1000 and 1400 CE, and they revealed a culture that was wealthy and religious and possibly played religiously-oriented sports.

3. Saeftinghe in the Netherlands, and yes, I know that my Dutch is excellent, was lost for centuries, though it's since been rebuilt and a full 55 people live there. The majority of the town was destroyed in the 16th century during the All Saint's Flood, which inspired the Dutch legend that the town was once very rich, but a fisherman caught a mermaid and refused to let her go, causing the flood and, uh, you know, the ensuing poverty and destruction and everything.

4. One of the largest Neolithic sites that you can still visit is Catalhoyuk, Turkey, which was a city from about 7500-5700 BCE. It was excavated in the 1950s, when archaeologists were looking for the home of the sea people from ancient Egyptian stories, and the buildings were so closely packed together that people probably walked on the rooftops of their houses rather than on pathways. The archaeologists found everything from ovens to murals to ladders used to get into the houses, and it's believed that 7,000 people once lived there.

5. Angkor, Cambodia was home to the capital of the Khmer Empire between the 9th and 15th centuries, and you can visit it now, but plan for a long visit, because at 400 square miles, it's bigger than the five boroughs of New York City. Experts aren't sure why the city was abandoned for Phnom Penh, but they believe it has something to do with the shift from Hinduism to Therevada Buddhism.

6. Speaking of capitals, Karakorum in Mongolia was the capital of the Mongol Empire during the 13th century. When it was excavated in the 1930s, archaeologists found that its citizens had heated floors, kilns, and methods for processing copper. We don't even have heated floors here in the mental_floss offices, we just walk around like peasants on regular carpet.

7. Persepolis in Iran has been there since 518 BCE, when it was the capital of the Achaemenid empire, basically home to a huge palace for the emperor. Half of the palace was an artificial terrace, meaning it was built on a mountainside. The city was eventually burned down by Alexander the Great, who burned down many great cities, though you can now visit the ruins of it at least.

8., 9. Calakmul can be found in modern day Mexico in the middle of a jungle, but it was once a Mayan city with about 50,000 citizens, known as the Kingdom of the Snake. The city even had a rival, the neighboring Tikal, because both wanted to be more powerful, and the two battled for centuries before the collapse of the Mayas.

Tikal, by the way, is in modern day Guatemala and features a temple that's 154 feet tall. Before the collapse of the Maya, the city may have had up to 90,000 citizens. By comparison, in 1350 CE, London had 50,000 citizens.



10. One of the biggest trade port cities in Egypt was Heracleion or Thonis. There's even a myth that Paris and Helen of the Trojan War visited Heracleion before the war began. For a long time, people believed that it was underwater, and in 2013, divers finally started finding artifacts from the city in the Mediterranean sea, including over 60 ships, gold coins, and huge statues. We have here a historic recreation. The astronaut isn't exactly in a diving suit, but it's close, and there was an anglerfish and a gigantic Viking girl. You know, it was about like this.

11. Speaking of the Trojan War, there are three interesting lost cities from Greece: Pavlopetri, Helike, and Chryse Island. Pavlopetri ruins are underwater thanks to an earthquake. It's believed that the city was around from about 2800 through 1000 BCE, and because of its size, some people believe that Pavlopetri inspired the myth of Atlantis, but I for one believe that Atlantis is real and it's out there and there are people living under the ocean right now. They're called Octonauts, and they're doing important work in the field of marine biology.

12. Helike was also underwater for a long time due to a tsunami in 373 BCE, which was blamed on Poseidon. Archaeologists found the ruins in 2001 CE because the lagoon covering Helike had dried up.

13. Chryse is really a lost island, not a city, but we're making an exception here. It vanished along with its supposedly amazing temple to Apollo, around the 2nd century CE. A diver claimed to have seen the ruins in the 1960s, but no further progress has been made, so all you explorers out there, if you're looking for a lost island to seek, check out Chryse. Although, frankly, if you're not already familiar with the lost island of Chryse, I'm a little bit concerned with your credentials as a lost island explorer.

Okay, let's finish up with some quick facts about various lost cities around the world.

14. Ubar, or the Atlantis of the Sands, is called that because it was once wealthy and powerful, and in 1992, it was supposedly found in Oman by a group of archaeologists, but experts still aren't sure if that's the true Ubar or if it's still lost.

15. The Maya city of Palenque in Mexico is 1,780 hectares and only 10% of it has been explored by archaeologists.

16. It's believed that the people in the Indus Valley who lived in Mohenjo-daro bred chickens not to eat, but because cockfighting was part of their religious rituals.

17. Kuelap in Peru was built in stages. The old parts are from around 600 CE, which is about three times as old as Machu Picchu, but the vast majority of the city was built between 900 and 1000 CE, about twice as old as Machu Picchu. Then the Inca conquered the people who built the city and added a bit more to it. The ruins are within a huge wall that's about 20 meters tall.

18. It's believed that Turquoise Mountain in Afghanistan was once a community where Jews, Christians, and Muslims got along and worked and lived together. Now, it's believed that the only thing left is a monument, Minaret of Jam.

19. But you can still visit the Great Stupa and a handful of Buddhist monuments from the lost Sanchi in India. Ashoka the Great commissioned the Great Stupa in the 3rd century BCE, making it the oldest existing Buddhist sanctuary.

20. You can also visit Troy, yes, that Troy, in Turkey. It was discovered in 1793, but scholars still debate the historical significance of the city and how real the story of the Trojan War actually is.

21. Cliff Palace in modern Colorado was a city made in the caves of a cliff by the Ancient Pueblo Peoples. About 100 people lived in the 150 rooms built into the cliff. The tribe left in around 1300 CE, possibly because of drought.

22. Cahokia in modern day Illinois was a Native American city that had a population of up to 40,000 people in the 13th century, meaning it was the largest city in U.S. history until Philadelphia in the 1780s.

23. Vijayanagar, India had around 500,000 citizens before it was destroyed in the 16th century. Before that, the city had multiple fields, gardens, markets, shops, and temples.

24. Great Zimbabwe was once home to a palace for the monarch in Zimbabwe. It took over 300 years for the city to be constructed after building commenced in the 11th century. The walls surrounding the city were 36 feet tall and covered 820 feet of distance.

25. And finally, I return to my salon to tell you about Pompeii, Italy. Mt. Vesuvius erupted in 79 CE, covering the entire city in about 15 feet of ash, which turned out to be pretty bad for both the city and its residents. Everything was destroyed—their amphitheater, aqueducts, cafes, brothels, a gymnasium, and multiple public baths. It was rediscovered in 1748, and there were people shaped casts frozen where they were when the volcano erupted.

Just a pleasant reminder from all of us here at mental_floss Video that life is fleeting and at any moment, a volcano could destroy us all. Thanks for watching mental_floss here on YouTube, which is made with the help of all of these nice people, and don't forget, Paper Towns, the movie based on my book comes out July 24, it's really good, I'm not just saying that. As we say in my hometown, don't forget to be awesome.