15 of History’s Greatest Mysteries

By their very nature, historical mysteries are tough to crack. After all, people have been trying to solve them for decades, if not centuries, and they’ve got nothing but reasonable theories (and plenty of unreasonable ones) to show for it. Eyewitnesses are usually long dead, and key evidence has been lost to the mists of time. Sometimes entire cultures have vanished, leaving no written records to explain their most remarkable achievements. Or maybe there was only ever one person who could lay the mystery to rest, and they’ve taken the answer to their grave. From geologic puzzles of deep time to unsolved crimes of the 20th century, here are 15 of history’s greatest mysteries—most of which remained unsolved to this day. 

1. Where is Cleopatra’s tomb?

Finding the burial place of Cleopatra VII, who is usually considered the last monarch of the Ptolemaic dynasty that ruled Egypt after the death of Alexander the Great—and therefore the last pharaoh of Egypt—would undoubtedly be one of the crowning archaeological achievements in modern history. The problem is, no one knows where to look. 

Conventional wisdom places Cleopatra’s tomb beside her palace in an area of ancient Alexandria that is now submerged beneath the Mediterranean Sea. If this is the case, the tomb is likely lost forever. 

But a few researchers have set their sights on Taposiris Magna, the location of a temple dedicated to Osiris, the Egyptian ruler of the realm of the dead, near Alexandria’s western outskirts. Since Cleopatra wanted to associate herself and her Roman lover, Mark Antony, with Osiris and his sister-wife, Isis, some believe it stands to reason that the two could be interred there. Excavations at Taposiris Magna were still underway in 2023, and have so far yielded 16 burial chambers, mummies with golden tongues, funeral masks, coins engraved with the legendary queen’s face, and a tunnel more than 4000 feet long—but no signs of Cleopatra.

If you’re especially captivated by the legend of Cleopatra’s tomb, you’re welcome to help look for it: The Taposiris Magna excavation has been turned into a hands-on tourist experience that starts at about $21,000 per person. 

2. What happened on the Mary Celeste?

If you’ve heard of the Mary Celeste, you can thank Arthur Conan Doyle. The unexplained abandonment of the ship in 1872—and the still-unknown fate of the 10 people aboard—might have been forgotten if not for Conan Doyle publishing a sensational short story about the fictional Marie Celeste in 1884 that captured the popular imagination and turned the American merchant ship into one of the most enduring maritime mysteries of all time.

In terms of solving the mystery of the Mary Celeste and the fate of its captain, his wife and 2-year-old daughter, and its seven-man crew, Doyle’s highly fictionalized account, involving a missing African artifact and a murderous mutiny led by a man who had been born into enslavement in America, was unhelpful. But the official inquiry conducted years earlier had also failed to come up with any reason for the crew to have abandoned a seaworthy vessel. There was three and half feet of water in the hold and a pump had been dismantled, and the ship’s lifeboat was gone. But the ship was safe and operable when it was found drifting near the Azores islands, and the crew who found it had no trouble sailing it 800 miles to Gibraltar to file a salvage claim. 

In 2006, a chemistry professor at University College London proposed a solution: A “pressure-wave type of explosion” caused by the ship’s cargo—around 1700 barrels of industrial alcohol—and some unknown spark had caused little damage but frightened the crew into abandoning the vessel. But other researchers have discounted the theory. While the mystery around the Mary Celeste remains unsolved, it continues to serve as inspiration for storytellers: Season 4 of True Detective was partially inspired by the abandoned ship as well as the Dyatlov Pass incident, another historical head scratcher. 

3. What caused the Great Unconformity?

In 1869, American geologist and explorer John Wesley Powell was working in the Grand Canyon when he noticed something strange: What should have been thousands of feet of rock were just hundreds, and as tools and techniques improved, it became clear that in parts of the Grand Canyon over a billion years’ worth of rock was missing. Since the missing time immediately precedes the Cambrian explosion—the period when evolution seems to have kicked into high gear and life on Earth suddenly and rapidly diversified—scientists would very much like to know more about it. 

Rock strata are full of gaps, or “unconformities,” but a billion years is a big one, even in terms of geologic time. As geologist Kalin McDannell explained to science mag Eos, it’s the difference between a book that’s missing a few pages and one that’s had entire chapters torn out. Whatever happened, it wasn’t a local phenomenon—since Powell noticed the anomaly in the Grand Canyon, it’s been spotted in other parts of the world as well. The gap is twice as large in some places, representing more than 40 percent of the planet’s history that just isn’t there.

So where did it go? Two main theories have emerged in recent years. The first maintains that the missing rock was scoured away by glaciers a few hundred million years ago, during what’s known as the Snowball Earth period. The other theory is a little more dramatic: The culprit might be Rodinia, a supercontinent that predates Pangaea and potentially sliced away huge swathes of what would become our geologic record as pieces of the enormous land mass broke away, slid around the planet, and smashed back together. It’s also possible that the Great Unconformity isn’t one gap, but many smaller ones caused by a series of distinct geologic events.

Whatever the cause, the Great Unconformity is a case of one mystery that might hold the key to another. Some researchers believe that when the missing rock was deposited into Earth’s oceans, it altered the chemistry of the water and seeded it with vast amounts of minerals and nutrients. This could have given early lifeforms the resources they needed to evolve helpful things like shells and skeletons, setting the stage for the Cambrian explosion.  

4. What’s up with the Salish Sea feet?

If you type the phrase Salish Sea into Google’s search field, the autocomplete feature assumes you’re going to ask it about all those feet. The phenomenon seems to have started in 2007, when a 12-year-old girl found a running shoe containing a human foot on a British Columbia beach. Since then, more than 20 disembodied feet, most of them secured in sneakers, have washed ashore on the Salish Sea’s U.S. and Canadian coastlines. The embarrassment of extremities has prompted sinister theories ranging from the somewhat plausible (a serial killer is clearly at work) to the fantastic (it’s obviously aliens). Science, however, has requested that we all calm down a little and consider the facts. 

For starters, authorities have ruled out foul play, determining that several of the feet belonged to people who died accidentally or by suicide. Roughly 8.7 million people live along these shores, and there’s a grim correlation between seaside population density and the number of corpses that end up in the water. But if it’s a natural phenomenon, why is it just feet? Why did it start happening so recently? And why just the shores around the Salish Sea? 

Science can help us here, too. The bodies of drowning victims—a category that would include most of the people who die in the waters of the Salish Sea—tend to sink, where their soft tissue is consumed by bottom-dwelling animals such as crabs and lobsters. Since soft tissue is much of what’s holding our feet on, they can easily become detached. If they’re tucked inside running shoes or hiking boots that are made of lightweight, buoyant materials—technology that began to develop rapidly around the time the feet started washing ashore—they’re likely to bob up to the surface, where the Salish Sea’s distinctive combination of geography, wind conditions, and currents conspire to deposit them on beaches rather than carry them out to the open ocean. For all intents and purposes, we can probably mark this one “solved.”

5. How—and why—were the Olmec Heads made?

Long before the Maya (at least the Classical Period of Maya) and Aztecs built sophisticated civilizations in what is now Central America and Mexico, the area was home to the Olmecs, a society that flourished around 3200 to 2400 years ago. As the first great civilization of Mesoamerica, the Olmecs are sometimes considered a “mother culture” that influenced many of the peoples who would come in their wake. They cultivated an extensive trade network and possessed impressive engineering skills, but we know them best for the spectacular art they left behind, including approximately 17 colossal stone heads that have been discovered to date. 

The mystery of the heads is two-fold. First, their size—some are nearly 10 feet tall, and they weigh about 8 tons on average—would have presented enormous logistical challenges. Each head is carved from a single volcanic basalt boulder, and each of those boulders had to be moved more than 50 miles from where it was sourced. How did they do it? And second, why did they go to all that trouble?

Given the resources and labor required to transport and create them and the fact that they appear to depict distinct individuals, most archaeologists think the heads are portraits of powerful Olmec rulers (though some have suggested they could represent ballgame players who were maybe not that good). As for how they were moved such long distances, several theories have been suggested, ranging from wooden rollers to enormous rafts to temporary causeways built specifically for their transport. Answering these questions would fill in some important blanks in our knowledge of human history, but so far researchers can only make educated guesses. 

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6. What happened to Roald Amundsen?

Exploration is a dangerous business. All 129 men who comprised the polar exploration venture known as the Franklin Expedition died in the years after the mission’s 1845 launch. The case of Amelia Earhart, the pilot who vanished with her navigator Fred Noonan while attempting to circumnavigate the globe in 1937, continues to make front page news despite little progress being made. We still don’t know what happened to British explorer Percy Fawcett, who vanished in the Amazonian jungle in 1925 while searching for the legendary lost city of Z, or Henry Hudson, who was placed in a small boat and cast adrift in waters off northeastern Canada following a mutiny in 1611.

The disappearance of legendary Norwegian explorer Roald Amundsen is a little different. Amundsen had certainly been at the forefront of polar exploration—he was the first to sail the Northwest Passage and, a few years later, he beat England’s Robert Falcon Scott to the South Pole by several weeks. But Amundsen didn’t die while charting new territory; he vanished on a rescue mission while trying to come to the aid of Italian pilot and aeronautical engineer Umberto Nobile, whose airship had crashed while exploring the Arctic in 1928. Amundsen’s own plane is thought to have gone down somewhere around Bear Island in Norway’s Svalbard archipelago. Fishermen found something strange in the area in 1933, but the object fell back into the sea before it could be recovered; a high-tech 2009 search came up empty. Amundsen’s fate remains a mystery, but according to Norway’s Roald Amundsen’s House, three objects that were recovered soon after Amundsen’s disappearance might suggest a crash south of Bear Island.

7. Who was D.B. Cooper?

No survey of historical mysteries would be complete without the tale of the man known as D.B. Cooper, the only person to have hijacked a commercial plane in the United States and gotten away with it (or at least evaded capture). Plenty of notorious criminals have managed to remain unidentified for decades or longer—we still don’t know the identities of Jack the Ripper, the Axeman of New Orleans, or the Zodiac Killer, to name a few—but Cooper belongs to a very different category. Other than showing a flight attendant a device he claimed was a bomb, his crime was nonviolent, and it was stunning in its boldness.

The day before Thanksgiving in 1971, Cooper boarded a flight from Portland, Oregon, to Seattle. A little after 3 p.m., he handed a flight attendant a note, flashed his supposed bomb, and made his demand: He was to be given $200,000 in cash and four parachutes, saying, “No funny stuff or I’ll do the job.” The plane landed in Seattle, traded its passengers and most of the flight attendants for Cooper’s ransom, and took off again.

As the plane flew over an area somewhere between Seattle and Reno, Cooper jumped into the cold, rainy night, buffeted by 200-mph winds, with nothing but the business suit (and possibly a trench coat) he was wearing, two parachutes, and $200,000 (a little more than $1.5 million in today’s currency). The ensuing manhunt, officially known as NORJAK, for “Northwest Hijacking,” lasted 45 years and yielded 800 suspects but no arrests. Cooper has become a folk hero to many, inspiring songs, movies, TV shows, podcasts, books, and even an annual gathering of enthusiasts known as “CooperCon.”

It’s likely Cooper didn’t survive the jump, which was so dangerous that an experienced parachutist would probably never have attempted it in the first place. In 1980, some of the ransom money was found near the Columbia River, leading some to suspect Cooper had perhaps parachuted into the water and died, but a 2020 study that examined diatom species on the recovered bills found they were exposed to water around May-June rather than November. Though the FBI officially dropped the case in 2016, amateur sleuths are still trying to crack the mystery. One theory even claims Cooper was a transgender woman named Barbara Dayton, who died in 2002 at the age of 76.

8. What happened to the lightkeepers of Flannan Isle?

There’s an entire category of historical mysteries devoted to vanishings—people who just seemed to disappear into thin air, leaving no physical clues about what might have happened to them. Jimmy Hoffa is probably the textbook example; nearly 50 years after he disappeared from the parking lot of a Detroit restaurant, his body still hasn’t been found. But 75 years before Hoffa met his fate, Scotland was investigating its own unexplained vanishing—three of them, in fact.

In December 1900, a steamship was passing by the Flannan Isles when its crew noticed the lighthouse had gone dark. Then, on December 26, a relief lighthouse keeper found the Flannan Isle structure abandoned. A search turned up no trace of the men, but there were signs that a violent storm had torn across the island: Supplies were strewn across the ground well above sea level, iron railings were twisted, and an enormous boulder had been dislodged. 

The subsequent investigation assumed the men had been caught in the storm and swept out to sea, but troubling details remained. For instance, if the men had ventured into the storm to secure equipment as had been assumed, why did one of them leave his raingear behind? A theory suggested by shepherds who grazed their sheep on the island connected the men’s deaths to a powerful marine spout that would sporadically shoot dangerous volumes of compressed seawater into the air. Perhaps one man stayed behind while the other two went out into a storm to secure equipment, saw from the lighthouse that conditions were right for the water to erupt, and rushed out to warn the others, only for all three to be swept out to sea in the storm. Others discount the compressed water explanation, but broadly agree that two of the men were outside doing something and for some reason the third man had to run outside in a hurry. A few years later, the poet Wilfrid Wilson Gibson invented stories of an overturned chair and partially eaten food, helping to create an enduring mystery.

9. Was King Arthur real?

The story of King Arthur is one of the most influential and widely studied literary cycles in Western culture, but there’s one big thing we don’t know about it: Did Arthur really exist?

There’s a vague reference to a legendary hero named Arthur in the Welsh poem Y Gododdin dated to around the 6th or 7th century, but it’s not that simple. The story survives in a couple different versions written centuries later, and only one of them mentions Arthur. Whether the Arthur reference is a 7th century original, a 13th century addition, or something in between is a contested area of scholarship.

The first explicit accounts date back to the 9th century Historia Brittonum, which documented 12 battles supposedly fought against the Saxons by a British military commander identified as Arthur. His feats were impressive, to say the least—in the 12th battle, he supposedly killed over 900 enemy soldiers all by himself.

Cleric Geoffrey of Monmouth built on Arthur’s legend in the 12th century with his History of the Kings of Britain, and subsequent Arthurian poems and romances added now-familiar elements such as the Round Table and the quest for the Holy Grail. It wasn’t until the 15th century that Thomas Malory came along and gave us what many now think of as the definitive story of King Arthur, Le Morte d’Arthur. 

When we ask whether Arthur really existed, it’s important to decide which version of him we’re asking about. If it’s the one that began with Geoffrey—a glorious king who once ruled most of Europe—the answer is probably no. If such a ruler had existed, odds are slim he would have been omitted from the historical record. But the Historia Brittonum’s earlier account of a great military leader called Arthur might have some basis in fact. The author probably got some of the details wrong—it would have been logistically impossible for one man to have fought in all 12 of the battles—but it’s not impossible that at some point in the dim and distant past there was a real military leader who rallied the fractured tribes of early medieval Britain against their Saxon invaders.

10. What happened to the Roanoke colony?

England’s plan to colonize North America did not get off to a smooth start. By the time artist-turned-explorer John White and about 115 colonists arrived on Roanoke Island off the coast of modern-day North Carolina in 1587, the settlement already had a reputation. It had been abandoned once in 1586, and a garrison of 15 men who were later deposited there, tasked with holding the land on England’s behalf, also disappeared, leaving behind nothing but a single skeleton to greet the next batch of colonists, who weren’t even supposed to be staying there. (The plan had been to proceed up to the Chesapeake Bay after stopping at Roanoke Island, but the conventional story is that the captain refused to go further.) There’s no reason to have expected White’s colony—which settled in an area where their recent predecessors had had trouble securing food, encountered formidable weather, and were quickly burning through any good will the Native American populations had shown them—would have fared any better.

The colonists arrived too late in the year to grow their own food, and White returned to England for more supplies. The first Anglo-Spanish War delayed his return, and when he finally got back in 1590, everyone was gone. But White didn’t seem puzzled by their disappearance. Someone had carved the word CROATOAN, the name of both a nearby island and the friendly Native American group who inhabited it, into a palisade post (or maybe a tree). White had instructed that if the colonists found themselves in distress, they should carve a type of cross alongside the location, but there was no cross—so he interpreted as a “certaine token of their safe being at Croatoan.” But a storm stopped him from sailing there to look for them, and he was never able to raise the money to finance another expedition to the New World. 

Hard archeological evidence for White’s proclamation “of their safe being at Croatoan” is still lacking. Most researchers think the settlers were either killed by Native Americans who’d turned hostile to European colonizers or, more likely, were absorbed into friendlier Native populations.  

According to archeologist Charles Ewen, the idea that there’s anything particularly strange about the colony’s disappearance might be a relatively modern development. “It’s no big mystery until you start to get a historical type of writing in the 1800s,” he told The New York Times in 2020, pointing out that failed colonization attempts were hardly out of the ordinary (though Ewen himself is skeptical of the Croatoan explanation for a lack of actual evidence). Science writer Andrew Lawler, author of The Secret Token: Myth, Obsession, and the Search for the Lost Colony of Roanoke, told Salon that “the ‘Lost Colony’ is a product of the 19th century”—a time, he says, when “the idea of the colonists assimilating with the Native Americans was a taboo.”

11. What was the English sweating sickness?

Between 1485 and 1551, England suffered five outbreaks of a disease so virulent that it could kill an otherwise healthy person in a matter of hours. Its favorite targets seemed to be wealthy adult males; children and elderly people were generally spared, while the aristocracy, members of professional classes, and the clergy seemed particularly vulnerable. The epidemics were short-lived but brutal, and in all but at most a handful of instances the disease did not spread beyond England.

Symptoms came on quickly; according to one account it came with “a sudden great sweating and stinking with redness of the face and of all the body” along with fever, headaches, and delirium. As many as half of those afflicted died within 18 hours. Anyone who made it through the first day would probably recover, but there was always a chance of reinfection.  

Whatever the disease was, it vanished as mysteriously as it appeared. The last outbreak was in 1551, and apart from some potential minor appearances in the following decades, we haven’t seen it since—though a similar affliction, known as the “Picardy sweat,” popped up in France a century and a half later, causing nearly 200 small outbreaks before it too disappeared in 1861.

Many theories have been floated over the centuries. It’s been suggested that the English sweating sickness could have been a strain of typhus or influenza, or even anthrax. A more likely answer emerged in 1993, when a similar outbreak occurred in the American Southwest. This disease was caused by a hantavirus, leading researchers to speculate that a hantavirus was also behind the English sweating sickness and the Picardy sweat. Since hantaviruses can be spread by rodents, this could explain why large households and academic institutions were hit so hard by the disease: Well-stocked kitchens and pantries would have attracted mice and rats, and household staff could have aerosolized the virus in their droppings while sweeping. This might be the best solution we get; according to a 2014 paper published in the journal Viruses, a conclusive answer will probably never come. 

12. What were the Nazca Lines for?

The Nazca (or Nasca) Lines are an array of geoglyphs carved into the coastal plain of southern Peru. Some are simply straight lines running in all directions, while others depict animals or people.

The lines were studied by researchers traveling on foot in the 1920s, but it wasn’t until commercial pilots began flying over the area in the 1930s that their full scope and elaborate design was revealed. According to UNESCO, the Nazca Lines are “unmatched in [their] extent, magnitude, quantity, size, diversity and ancient tradition to any similar work in the world.” They were built over the course of 1000 years, mostly by removing darker stones to reveal the lighter colored sand underneath. 

The question that still puzzles researchers is, why were the geoglyphs made? For decades, some archaeologists believed they served as giant astronomical calendars, possibly linked to constellations or other celestial bodies. Recent research suggests a more earthly purpose: It now appears that the Nazca Lines might have been connected to rituals meant to appeal to the gods for rain. It’s possible they marked processional routes used by pilgrims as they traveled to temples, or that rituals were performed at designated points along the lines themselves. 

13. What does the Voynich Manuscript say?

We don’t know when, where, or by whom the Voynich Manuscript was written, but there’s an even larger mystery to solve: We have absolutely no idea what it even says. The text—which is accompanied by astrological charts, illustrations of strange plants and naked, possibly pregnant women emerging from tubes and funnels or wading in green fluid, and other bizarre images—is composed in a writing system that doesn’t appear on any other document or object we’ve discovered so far. Some, including the late U.S. Army cryptographer William Friedman, believe Voynich was written in a synthetic language. Others think the manuscript uses a dead language such as proto-Romance, a precursor of vulgar Latin (though that claim was highly controversial), or that it could be written in some form of code or cipher. 

Whatever the case, the book is divided into six sections: one devoted to botanical studies; one that is apparently concerned with astrological and astronomical matters; one that contains elaborate (and super weird) biological drawings; a section containing what Yale University, the book’s keeper since 1969, identifies as “cosmological medallions”; a section dedicated to pharmaceutical sketches; and a text-only portion devoted to what appear to be recipes. 

Since bookseller Wilfrid Voynich found the manuscript in 1912, secreted in a bundle of medieval manuscripts he’d purchased from a Jesuit college, the book and its complicated history have been obsessively studied and analyzed. Carbon dating tells us the manuscript’s vellum was sourced in the early 15th century; pigments are consistent with that date as well, so that’s presumably when it was written. We know (or at least we think we know) it’s been owned by a Holy Roman emperor, an alchemist, a famed Bohemian doctor, and possibly Elizabethan occultist and court astrologer John Dee. If any of its previous custodians figured out how to read it, they kept it to themselves, but you’re welcome to give it a go if you’re feeling froggy. 

14. Who built Stonehenge?

Since the 17th century, the popular imagination has linked Stonehenge to the Druids, but the timeline doesn’t shake out—the earliest historical references to the Druids date to the 4th century BCE, while Stonehenge was most likely built sometime between 3000 and 2000 BCE. But if the Druids didn’t build it, who did?

There might not be one simple answer. Construction of Stonehenge is thought to have taken place in several phases over the course of about 1500 years. The first monument at Stonehenge simply consisted of a circular earthwork that enclosed dozens of pits and possibly some rocks. The iconic stone slabs were added a few hundred years later—around the same time the Egyptians were building the pyramids at Giza. It’s long been thought that Neolithic hunter-gatherers got the ball rolling, but new evidence suggests Stonehenge’s builders were the descendants of Mediterranean farmers who migrated to northwestern Europe 6000 years ago. 

Whoever Stonehenge’s builders were, their accomplishments were astonishing. We’re still trying to figure out how Stonehenge was constructed; some of the stones came from nearby quarries, but others were sourced from a Welsh site 200 miles away. We have no idea how people who didn’t even have wheels were able to transport the stones and hoist them into place.

15. Who killed the Black Dahlia?

History is full of unsolved murders, from the disappearance and presumed assassinations of King Edward V and Prince Richard, Duke of York, in 1483 to the Zodiac killings that terrorized the Bay Area in the 1960s. But none has captivated American popular culture quite like the horrific murder of Elizabeth Short, the young woman who will forever be known by the sensational nickname given to her by the press: the Black Dahlia.

Short’s body was discovered on January 15, 1947, in a vacant lot in Los Angeles. The brutality that had been visited upon her, both pre- and post-mortem, is still shocking: Her face had been grotesquely disfigured, her body cut in half, and some of her organs removed, among other acts of torture and mutilation. No one was ever arrested for Short’s murder, and the case eventually went cold. Recent theories have blamed everyone from Orson Welles to Bugsy Siegel. 

The Los Angeles Police Department investigated dozens of suspects, including George Hodel, a surgeon whose social circles included surrealist photographer Man Ray and The Maltese Falcon director John Huston. Upon learning his father had been investigated for the murder, George’s son, Steve, decided to clear his dad’s name after his dad’s death in 1999, only to become convinced that George was indeed Short’s killer. Steve published his findings in a well-received and fairly convincing 2003 book, but later lost some credibility when he also accused his father of being the Zodiac Killer.

In 2018, British author Piu Eatwell also claimed to have identified Short’s killer. In her book Black Dahlia, Red Rose, Eatwell maintains that the culprit wasn’t one murderer but a group of conspirators that included a bellhop and former mortician’s assistant named Leslie Dillon (who had been one of the LAPD’s favorite suspects decades ago), nightclub owner Mark Hansen, and a man named Jeff Connors. Eatwell thinks the police were involved in a cover-up due to their connections with at least one of those men, though she allows that the case will probably never be definitively solved.