We’re pretty sure you’ve heard of the lost city of Atlantis but have you ever heard of Paititi? Paititi, the legendary lost Inca city that is supposed to be full of gold and other riches, allegedly lies east of the Andes, hidden somewhere within the remote rain forests of southeast Peru, northern Bolivia, or southwest Brazil.

The Parthenon is one of the most iconic and prized structures of Western civilization, but there are many mysteries surrounding it. For example, how did the ancient Athenians carry all that marble from Mount Pentelicus and build this masterpiece with primitive tools and resources available at the time? How did they achieve such flawless proportions and balance? How did they conceive of and form such subtle visual elements? How did the workers work with such precision, sometimes accurate to within a fraction of a millimeter (when even modern computers fail), without the help of modern technology? After 2,500 years we still don’t know.

There are numerous mountains with features such as flat tops, mysterious straight lines, and fascinating ancient drawings; however, the Palpa Flat Mountain houses one of the most impressive display of such features. The “strips” on the surface of this mountain appear as though they were literally “drawn” by a giant with a spray gun directly from above.

In what is undoubtedly the biggest mystery of this decade, MH370 vanished with 239 people on board on March 8, 2014, on its way to Beijing from Kuala Lumpur. Despite the ongoing searches and some of the world’s most powerful countries, including Russia, China, France, and the United States, sending some of their best investigators to shed light on the case; we still have no clue what happened that day.

On the early morning of 9 February 1855, people in towns across southern Devon, England, awoke to find a single line of hoof-like marks in the deep snow as if they had been branded with a hot iron. The Times said the marks were found over a distance of 40 miles on both sides of the Exe, as if “some strange and mysterious animal endowed with the power of ubiquity” had created them during the night. The footprints were called the “Devil’s footprints” because some people believed that they were the tracks of Satan, as they were allegedly made by a cloven hoof. Many theories have been put forward to explain the incident, but not one can explain all the reported marks and the mystery remains to this day.

Hinterkaifeck was a small farmstead situated between the Bavarian towns of Ingolstadt and Schrobenhausen in Germany that became well known in 1922 when its six inhabitants were murdered with a mattock. The murder remains unsolved to this day.

In July 1518 many people—most of them unknown to each other—from the city of Strasbourg, France (then part of the Holy Roman Empire), were struck by a sudden and seemingly uncontrollable urge to dance. The hysteria kicked off when a woman known as Frau Troffea stepped into the street and began to silently dance. Before she knew it dozens of people had joined her and a month later the dancing epidemic had claimed as many as four hundred victims. With no other possible explanation, local physicians blamed it on “hot blood,” but no accurate scientific answer has been found.

On August 15, 1977, Jerry R. Ehman received an unusual seventy-two-second signal (while working on a Search for Extraterrestrial Intelligence (SETI) project at the “Big Ear” radio telescope at Ohio State) that went down in history as the “Wow! signal.” Several astronomers worldwide have tried to find the signal again. What was it exactly? We don’t know?

Jack The Ripper: Despite being the most notorious—even though nowhere near the deadliest—serial killer of all time, his identity remains unknown to date. Many theories have popped up throughout the years, with some of them being truly insane, but no investigation has led to a safe conclusion.

On June 24, 1947, private pilot Kenneth Arnold claimed he saw a string of nine shiny unidentified flying objects flying past Mount Rainier. This sighting is considered the most popular of the modern age and is credited with starting the paranoia over possible UFO sightings. Arnold’s description of the objects also led to the press quickly coining the terms “flying saucer” and “flying disc,” phrases that have been widely used for UFOs ever since.

“D. B. Cooper” is the nickname the American media widely used to refer to the unidentified man who hijacked a Boeing 727 in the airspace between Portland, Oregon, and Seattle, Washington, on November 24, 1971. He took with him about $200,000 in ransom (equivalent to $1,170,000 in 2016) when he parachuted from the plane to an unknown fate. The case remains the only unsolved air piracy in American aviation history. Cooper’s real identity also remains a mystery.

The Dyatlov Pass incident involved a group of nine experienced ski hikers from the Ural Polytechnical Institute and took place on the night of February 2, 1959, in the northern Ural Mountains. Due to the lack of survivors the chronology of events remains uncertain and the Soviet authorities determined that an “unknown compelling force” had caused the skiers’ deaths. Some of the bodies were found barefoot, some were quite butchered, others were physically unharmed but had severe brain damage, and a woman’s tongue was missing. Although several possible explanations have been put forward, a violent encounter with a yeti or other unknown creature seems to be the most logical.

On the morning of December 1, 1948, a body was found on the shore of Somerton Beach. The man was resting against the seawall, slumped forward, with a half-smoked cigarette lying on his lapel. He was well dressed, in a suit with shined and heeled shoes—odd attire for the beach. There was no sign of violence or a struggle and the man’s identity remains unknown to this day.

At the dawn of the Space Race, the United States and the Soviet Union were in a head-to-head race to claim technological supremacy, but as mission after mission wrenched the secrets of the universe from the stars above, rumors began to circulate that some of the astronauts who were rocketed into the skies above never returned. These people became known as the Lost Cosmonauts and the whole thing became big news when two amateur radio operators received transmissions from Sputnik and heard Russian cosmonauts in agony saying that they were going to crash and die. Of course, the Soviet authorities denied they had sent any cosmonauts into space and debunked the whole thing as a hoax but no one knows what really happened.

When someone takes a look at the photos of some ancient paintings that clearly depict aliens and/or alien spacecraft they can’t help but think either science fiction fandom has been around since the dawn of humankind or there were real ancient astronauts, aliens, and spacecrafts out there in the universe before our own space journeys began in the 1950s. We don’t know which is true really, but we have to admit it’s a lot harder to disbelieve that something otherworldly once lived and walked among us than the sci-fi fandom scenario.

Is there really a pyramid on the moon? Looking at the original image taken during Apollo 17’s 1972 mission, you can easily notice a triangular-shaped object, but is this enough evidence to say that there is a pyramid on the moon? If, however, there is a pyramid on the moon then we should ask two important questions: Who made it? And what is its connection, if any, to the pyramids here on Earth?

The theory of the “Black Knight satellite” emerged after several NASA pictures were released following the 1998 Endeavor space shuttle mission to the International Space Station. According to some people, the Black Knight satellite is an object approximately thirteen thousand years old of extraterrestrial origin orbiting Earth in a near-polar orbit. Critics and many academics have called it a conspiracy theory and an urban legend.

Bouvet Island is an uninhabited subantarctic volcanic island located in the South Atlantic. It is the most remote island in the world and all you can find there are miles of volcanic basalt groaning under several hundred feet of glacier, scraped raw by gales and shrouded by sea fog. The strange thing about this unearthly landscape is that an abandoned lifeboat was found there, raising a number of questions. Who managed to get there with a lifeboat? When did this happen? What happened to the person or people on the boat since no human remains have been found there?

The identity of “the Babushka Lady” may never be truly pinned down, despite being the only person who might have photographed the events that occurred at Dallas’ Dealey Plaza when John F. Kennedy was shot. There’s no photograph that shows her face, and we still don’t know if her presence there was coincidence or if she played a significant role in the assassination.

Hitler’s “stolen treasure” is supposed to be one of the biggest caches of all time. It includes gold bars, jewelry, and foreign currency, with an estimated value of $4 to $5 billion. However, the stolen Nazi treasure disappeared in the blink of an eye from the vaults of the German Reichsbank. In the years that followed World War II, it was reported that part of the treasure was found in Portugal, Switzerland, and Spain, among other places, but these pieces hardly compare in value to the supposed hoard as a whole.

On November 19, 1703, a tomb in the Bastille’s Saint Paul Cemetery welcomed the corpse of a man who had spent almost all of the last four decades of his life in various prisons in France. He is without a doubt the most famous prisoner in French history, even though nobody knows why he had to spend over thirty-five years in jail, reportedly in near-perfect isolation and often with his face covered. Who was this man and why did he have to endure this long, terrible imprisonment? Was he the older twin of France’s king (and thus the legitimate king of France) as some theories suggest?

Rudolph Fentz was the main and controversial character of “I’m Scared,” an early 1950s science fiction short story by Jack Finney, which was later revealed to be based on true events. The story tells of a man who’s dressed in nineteenth-century clothes when he is hit by a car and killed in New York City in 1950. A subsequent investigation revealed that the man had disappeared without a trace in 1876, and the items in his possession appeared to reveal that the man had traveled through time from that year to 1950. Truth or fiction? We will never know for sure.

Back in 1959 a shepherd came across a small opening to a cave in northern Greece, which became visible when a thick covering of snow finally melted. Surprisingly, one of the findings included a human skull embedded in the wall, the so-called Archanthropus of Petralona, as it has been termed. It was found to be 700,000 years old, making it the oldest human europeoid. The biggest surprise of this discovery was that Dr. Poulianos, a member of UNESCO’s International Union of Anthropological and Ethnological Sciences (IUAES), found that the Archanthropus of Petralona evolved separately in Europe and was not related to any species that came out of Africa, thus challenging the “out of Africa” theory. What’s the strangest thing of all, though? Every Greek government has banned further research regarding this incredible discovery and has closed the case.

One of the most enduring legends of Roman Britain concerns the disappearance of the Ninth Legion. The idea that five thousand of Rome’s finest soldiers were lost in the swirling mists of Caledonia as they marched north to put down a rebellion sounds unbelievable, but the fact remains that not a trace of one has ever been found, nor has any spear, shield, or anything else turned up to indicate that there had been a battle.

In July 1954 a Caucasian man who looked pretty normal arrived at the airport in Tokyo. When he had his passport checked, however, the Japanese authorities were stunned to find that he hailed from a country called Taured, a country that doesn’t exist. His passport looked genuine and when they asked him to show them his country on a map, he automatically pointed at the Principality of Andorra. When he saw that his homeland of Taured wasn’t on the map he became furious and insisted that his country existed for more than a thousand years. Japanese police took him to a local hotel and placed him in a room with two guards outside until they could get to the bottom of the mystery. A few hours later when they went into his room the man was gone, even though the guards never left and the room had no balcony or another exit for him to escape through. Was the man from Taured lost in our world from another parallel universe or dimension? We will never know since he was never seen again.