Genevieve Carlton

Updated 2019 Sep 20

Though people pretend it’s written in stone, history features tons of famous mysteries – many of which remain unsolved. From the location of Genghis Khan’s tomb to the instructions for making a Byzantine weapon that inspired Game of Thrones, this list collects the best-kept secrets in history. Some secrets remained hidden for centuries until an accident uncovered them, such as a solid gold Buddha hidden in plain sight. Surprisingly enough, that’s not the only million-dollar secret on this list. Other top-secret information, from the Manhattan Project to Britain’s World War II intelligence operations, eventually came out after the war, stunning the public.

From the many unsolved ancient mysteries that still baffle people to all those shady government cover-ups, historians have shared history’s most explosive secrets on Reddit. And more than one of these secrets even changed the course of the world. Some of the unanswered questions in history still make headlines today, including the identity of the man in the iron mask or what certain mysterious Egyptian hieroglyphics mean.

When you dive into history’s best-kept secrets and biggest questions, don’t expect many answers.

              Khan is listed (or ranked) 1 on the list Historians Reveal
              History's Best Kept Secrets
Photo: Anonymous/Wikimedia Commons/Public Domain

From Redditor /u/GoGoButters:

The location where Genghis Khan was buried [is unknown]. Legend has it that his funeral escort killed anyone they passed in order to conceal the burial site. There are speculations on the where Genghis Khan was buried, but no one has found it.

Conqueror Genghis Khan died over 800 years ago, and despite many searches, no one has located his tomb. And the Mongol ruler wanted it that way: he asked for a secret burial, even ordering his army to hide the location by killing anyone they passed during his funeral procession.

According to legend, his soldiers rode 1,000 horses over the grave to make sure no one would discover it. And while most agree his tomb resides in Mongolia, that still leaves a space roughly seven times the size of Great Britain to search.

Among Mongolians today, there exists little interest in uncovering the tomb. Many people consider searching for Khan’s grave a sign of disrespect – he never wanted to be found, and they wish to honor the conqueror’s final request.

A Solid
              Gold Buddha Once... is listed (or ranked) 2 on the list
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A Solid Gold Buddha Once Hid In Plain Sight

From Redditor /u/Brackto:

The “Phra Phuttha Maha Suwan Patimakon,” a nine-foot tall stucco Buddha statue, was actually solid gold underneath.

For over 600 years, a 9-foot-tall stucco Buddha statue sat in Bangkok, Thailand. Known as the Phra Phuttha Maha Suwan Patimakon, it was so heavy that it sat outside for years, with a simple tin roof covering the statue. Then, in 1955, the statue was accidentally dropped while being moved to a new location. Pieces of the stucco broke off, and the shocked onlookers realized the entire Buddha was solid gold.

Worth an estimated $250 million, the statue may have been covered with stucco to protect it from Burmese invaders back in the 1700s. The ploy worked in that case, as no one noticed for centuries.

No One
              Knows How To Make... is listed (or ranked) 3 on the list
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Photo: Unknown/Wikimedia Commons/Public Domain

No One Knows How To Make This Byzantine Secret Weapon

From Redditor /u/quiaudetvincet:

Greek Fire… was essentially gasoline for flamethrowers that was used by the Byzantine Empire from around year 670 to their final fall in 1453. The fire was also not only able to still burn on water, but seemed to be fueled by water, with the flames spreading even more as people tried to put it out. So the Byzantines strapped these flamethrowers to their vessels to simply burn enemy ships before they even got close.

But the ingredients for this flammable jelly were such a closely guarded secret by the empire that no one knows just what the stuff was made of, and any efforts to recreate it haven’t been successful so far.

Greek fire, sea fire, liquid fire: the Byzantines invented a weapon so perilous that it could only be extinguished with sand or vinegar. And for over a thousand years, no one has been able to replicate the secret recipe.

The Byzantines deployed the weapon using a pump to douse enemy ships, or they sealed it up inside clay pots to throw like grenades. The concoction even inspired a fictional version of the weapon: wildfire in Game of Thrones.

Man in
              the Iron Mask is listed (or ranked) 4 on the list
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Photo: Anonymous/Wikimedia Commons/Public Domain

From Redditor /u/Eurymedion:

[No one knows] the true identity of the Man in the Iron Mask.

In the 1680s, King Louis XIV ruled France as an absolute monarch, even imprisoning a man for life who was locked in an iron mask to hide his identity. But who was the man in the iron mask, later made famous in a novel written by Alexandre Dumas?

Could he be the Sun King’s own child? Or the king’s cousin, who plotted revolt against the monarch? Or, as Dumas and Voltaire theorized, the king’s twin brother, locked away and hidden to protect the ruler’s legitimacy?

The mystery lingers, although one historian claims most serious researchers believe the prisoner was a lowly valet – but he and the others can’t explain how the man earned such a punishment.

Tutankhamun is listed (or ranked) 5 on the list
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Photo: The New York Times/Wikimedia Commons/Public Domain

King Tut’s Tomb May Not Have Been His Planned Resting Place

From Redditor /u/ConneryFTW:

[No one knows] where King Tut was buried. To my knowledge he’s the only Pharaoh whose tomb wasn’t plundered (until modern times).

King Tut died over 3,000 years ago, but his tomb evaded archaeologists until 1922, when Howard Carter uncovered his burial chamber in Egypt’s famous Valley of the Kings. Archaeologists mistakenly believed they found every pharaoh’s tomb, but Tut’s proved unsullied by looters.

Why was King Tut’s tomb untouched for millennia? One theory claims the tomb wasn’t designed for a pharaoh at all, but when Tut died suddenly as a teenager, it was used for his burial.

No One
              Knows The Volcanic Secr is listed (or ranked) 6 on the
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Photo: Jaakko Luttinen/Wikimedia Commons/CC-BY-SA-3.0

No One Knows The Volcanic Secret To Rome’s Concrete Recipe

From Redditor /u/NotoriousTNT:

The ancient Roman formula for concrete [was] so closely guarded that to this day we still aren’t 100% certain what the recipe was. It allowed them to build domes, which was borderline miraculous for the times.

Ancient Rome’s most magnificent structures, the Colosseum and the Pantheon, still stand in the city today. That’s thanks, in large part, to the Roman recipe for concrete, which remains something of a mystery even 2,000 years later.

Researchers know the Romans mixed volcanic ash into their concrete, and they sometimes used saltwater to strengthen it. And this recipe allowed the Romans to build monumental, long-lasting architecture.

Franklin D. Roosevelt is listed (or ranked) 7 on the
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Photo: Frank O. Salisbury/Wikimedia Commons/Public Domain

From Redditor /u/YouBoxEmYouShipEm:

FDR’s polio/reliance on a wheelchair was kept pretty well under wraps from the public.

There’s even a tunnel that was built from Grand Central Terminal to the Waldorf Astoria so he could be transported by wheelchair without the public seeing.

President Franklin Delano Roosevelt did everything he could to keep descriptions and images of his wheelchair out of the press. After surviving polio but losing much of the use of his legs at age 39, Roosevelt didn’t want to publicize his disability, and the Secret Service allegedly helped keep the press at bay. According to Time:

As Editor & Publisher reported in 1936, if agents saw a photographer taking a picture of Roosevelt, say, getting out of his car, they would seize the camera and tear out the film. “By what right they do this I don’t know,” the correspondent wrote, “but I have never seen the right questioned.” A 1946 survey of the White House photography corps confirmed this, finding that anyone the Secret Service caught taking banned photographs “had their cameras emptied, their films exposed to sunlight, or their plates smashed.”

Still, some outlets reported on the extent of FDR’s use of mobility devices, and a few even published photos of him using his wheelchair. Time reports that, throughout the 1930s and early 1940s, at least five articles in prominent newspapers and magazines printed accurate descriptions of Roosevelt’s mobility.

Roosevelt even used an existing private train terminal under the Waldorf Astoria hotel in New York to his advantage: when traveling between Washington and New York, Roosevelt’s locomotive stopped at the Waldorf platform, where he could exit the train and travel directly to his room. Contrary to popular belief, Roosevelt didn’t commission the station specifically to hide his polio; the hotel owners had it built at the same time as the hotel. But Roosevelt did utilize the station during his time as President, according to Secret Service logs, and his private train – long since abandoned – still sits in the tunnel to this day.

No One
              Can Fully Crack The Sec is listed (or ranked) 8 on the
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No One Can Fully Crack The Secret Of Egyptian Hieroglyphics

From Redditor /u/Attican101:

Even though we have figured out one form of the hieroglyphs being the base system for taxes etc there are other meanings to each glyph we have no idea of and can only guess at.

For centuries, Egyptian hieroglyphs presented a mystery, a code that could not be cracked. In the 1820s, the Rosetta Stone helped scholars learn some hieroglyphic symbols, revealing they were not an alphabet at all, but rather symbols that could represent sounds or words.

While modern scholars have unraveled the secret of many symbols, some remain a mystery.

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Photo: Benjamin Tallmadge/Wikimedia Commons/Public Domain

From Redditor /u/chevdecker:

The Culper Ring, a network of spies hand-picked by George Washington to spy on the British in the Revolutionary War. Took over 150 years for anyone to figure out who any of them were.

George Washington was a general, the first US president, and the leader of a secret spy ring. The Culper Spy Ring, founded by Benjamin Tallmadge, provided invaluable intelligence information for the general as he battled the British troops during the American Revolution. By getting close to loyalists in the colonies and enemy forces on Long Island, the spies discovered and passed on intelligence regarding British troop movements, enemy fortifications, and secret British plans to attack the French army.

Washington, also known as Agent 711, may have won the war thanks to his spies.

              Romans Used Herbal Bir is listed (or ranked) 10 on the
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Ancient Romans Used Herbal Birth Control

From Redditor /u/senolimpiar:

[No one knows the] Roman recipe for birth control. It’s from a reed that is believed to be extinct.

Roman doctors got a lot of practice with two things: war and sex. According to scholars, they even developed a birth control method that relied on a secret recipe using silphium, an herb similar to fennel. The rare plant, which grew in North Africa and the Romans couldn’t cultivate, soon became extremely valuable. In fact, it became so valuable that the Romans drove it to extinction, destroying their recipe for the rest of time.

There remains debate on how effective the plant was at its intended purpose, but the modern world will never know.

              Unclear How China Maintai is listed (or ranked) 11 on the
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It’s Unclear How China Maintained Its Valuable Silk Road Monopolies 

From Redditor /u/Ginkgopsida:

Porcelain slowly evolved in China and was finally achieved (depending on the definition used) at some point about 2,000 to 1,200 years ago, but Europeans could only replicate it since about 1700.

China enthralled the rest of the world with its beautiful porcelain and silks, which the country sold on the Silk Road for centuries. Other countries, mainly Western European nations, clamored for the secret process behind making “white gold” and porcelain, but were unable to unlock the secret.

China successfully maintained a monopoly on silk for years, with silk production only reaching Korea in 200 BCE before slowly moving to Europe, when Italy first established the practice around 1100 CE.

China maintained its monopoly on porcelain even longer, until Europeans unlocked the secret in the 1500s and began mass-producing it around the 1700s.

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The Manhattan Project Cost Billions, But Remained Secret

From Redditor /u/derdody:

Considering the size and cost, [how was] the Manhattan Project [kept secret?]. The toughest part? Hiding 3 billion 1940s US dollars from Congress and especially the war efficiency guru Harry Truman. Yes, there were holes (Fuchs, etc), but damn if they didn’t pull the thing off. No question about that, right or wrong.

Even before it entered World War II, the United States began undertaking an ultra-expensive, ultra-secret initiative code-named the Manhattan Project. The goal was to create a weapon more destructive than anything ever built, one to combat Nazi Germany, where the US correctly feared Hitler was trying to develop one of his own. It had to remain top-secret, despite employing 130,000 people, being conducted in 30 different sites, and running up a bill of over $2 billion dollars – the equivalent of at least $27 billion today.

Shockingly, the United States developed an atomic bomb with near perfect secrecy.

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British Intelligence Invented A Fake Man To Trick The Nazis

From Redditor /u/Slide_Jeremy:

[During] Operation Mincemeat, the British SOE [Special Operations Executive] created a fake ID for the corpse of a homeless man cleaned up to look like a naval officer and attached a briefcase full of fake plans for an invasion of Greece to his wrist before having the body wash up on shore in [Spain]. Admiral Wilhelm Canaris, the head of the German Abwehr (military intelligence), had been feeding Britain intelligence information since 1939 and made sure that the plans were taken seriously by the German military command. The Western Allies next move would be the invasion of Sicily (Operation Husky) instead on 9 July 1943.

The British boasted a number of intelligence advantages during World War II, including cracking the Enigma Code. They also managed to keep many secrets during the war, including the ambitious Operation Mincemeat, which involved Ian Fleming, the creator of James Bond.

During that operation, the British government disguised the cadaver of a homeless man as a naval officer, allowing his body to wash ashore in Spain for the Germans to find. Along with a briefcase of documents showing a planned invasion of Greece by the British, the decoy managed to throw off Axis powers about Allied invasion plans.

By distracting the Germans with plans showing an invasion in Greece, the British managed to invade Sicily successfully.

Greek              And Roman Mystery Cults is listed (or ranked) 14 on the              list Historians Reveal History's Best Kept              Secrets
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Greek And Roman Mystery Cults Practiced Secret Rites Underground

From Redditor /u/mynameisevan:

[Some] Greco-Roman mystery cults… were around for almost 2,000 years, but they died out when Christianity started to take over. We don’t know much of anything about what mysteries they taught because that stuff was secret and they didn’t write any of it down.

Ancient Greece and Rome saw the rise of many mystery cults, some of which met underground. Very few historical sources contain reliable information on these cults, thought to focus on the afterlife. While theories claim they practiced a type of proto-Christianity, most scholars acknowledge the groups undertook a variety of practices and purposes, with initiation rituals, magical rites, and sacred images.

Many of the mystery cults vanished after Roman emperor Theodosius outlawed polytheism and destroyed temples in 391 CE.