YOU’VE ALREADY HEARD OF THE mystery of Amelia Earhart: the trailblazing golden-age pilot who mysteriously disappeared in 1937 during a circumnavigation of the globe. But Earhart is hardly the only traveler to have set out on a journey only to have vanished into thin air. Here are 5 other travelers who went out exploring — and never came back.

1. Ambrose Bierce

Ambrose Bierce was an all-around badass. The author basically invented the twist ending with his classic short story An Occurrence at Owl Creek Bridge, he inspired generations of horror writers with his creepy stories like An Inhabitant of Carcosa, and he became one of the world’s most eloquent misanthropes, writing the classic Devil’s Dictionary, and going by the motto, “Nothing matters.”

But he was also a kickass journalist. Late in life, he went to Mexico to report on the escapades of Mexican revolutionary Pancho Villa. The last trace of him was a letter sent to a friend the day after Christmas reading, “As to me, I leave here tomorrow for an unknown destination.” Bierce was never seen again.

Rumor in Mexico is that he was executed by firing squad in a cemetery (he was known to be critical of Pancho Villa), but there has never been any proof of this. Despite hundreds of theories, there has never been any substantial proof as to what happened to the great Ambrose Bierce.

2. John Franklin and his crew

In the 19th Century, the British Empire was insistent on discovering the Northwest Passage — the fabled route from the Atlantic to the Pacific over the top of Canada. But what they didn’t know was that the route was almost always covered with pack ice.

One of the most infamous expeditions sent to discover the passage was that of Sir John Franklin. The expedition, made up of two boats, the Erebus, captained by Sir John, and the Terror captained by veteran sailor Francis Crozier, and made up of 127 crewmen, sailed into the winter ice in 1846 and became trapped. The ice didn’t thaw the next summer, and, after spending two winters there (and after losing 24 men, including Franklin, to disease, accidents, and scurvy), Captain Crozier took the remaining men out over the ice in a mad dash for civilization.

They were never seen again. Inuit gave reports of wandering, starving men who refused to ask them for help, and said that the men had resorted to cannibalism to survive. Some reported that Crozier and another crewman had survived and were near Baker Lake, some 250 miles away, nearly a decade later, but what really happened mostly remains a mystery — though the sunken Erebus was discovered underwater in 2013.

Frank Lenz

Frank Lenz was basically the Amelia Earhart of cycling. He was a Philadelphian cyclist, and he decided he wanted to ride his bike around the world. Although it had already been done once before, a magazine hired Lenz to do it himself in 1892, as Lenz was an excellent photographer and would be able to capture the trip on film.

He started in Washington, D.C., and peddled to San Francisco, where he caught a boat to Japan. From there, he biked through China and through the dense, almost impassable jungles of Burma. From there, he rode through modern day India and Pakistan (then part of the British Empire), and then into what is now Iran.

He was last seen in Tabriz in Iran, peddling out of the city towards Erzurum in Turkey. He was never heard from again.

Percy Fawcett

Percy Fawcett might be the swashbucklingest person to have ever lived. The British Lieutenant Colonel and archaeologist was the inspiration for Arthur Conan Doyle’s The Lost World, and that other swashbuckling archaeologist you may have heard of, Indiana Jones.

In his 30s, he became fixated on the mythical “Lost City of Z,” sometimes popularly known as the golden city of El Dorado. With his son and his friend, he set off into the Brazilian Amazon to find the city in 1925. His final letter, sent from the jungle, read, “You need have no fear of any failure…”

The nearby Kalapalo tribe passed down an oral story of three explorers who came into their village one night and stayed for a while. The explorers then moved on, and for five days, the Kalapalo could see the smoke from their fires. On the fifth day, the fires stopped. No one knows what happened after that.

Ettore Majorana

Ettore Majorana was a famous Italian physicist who worked with the likes of Heisenberg, Bohr, and Enrico Fermi (who called him a genius). He was known for his work on neutrinos, and was considered a brilliant mind, but his health was poor, and in his later years, he became a hermit. In 1938, one day, while he was living in Palermo, he withdrew all of his money from his bank account, and sent this letter to the director of his University:

“Dear Carrelli, I made a decision that has become unavoidable. There isn’t a bit of selfishness in it, but I realize what trouble my sudden disappearance will cause you and the students. For this as well, I beg your forgiveness, but especially for betraying the trust, the sincere friendship and the sympathy you gave me over the past months. I ask you to remember me to all those I learned to know and appreciate in your Institute, especially Sciuti: I will keep a fond memory of them all at least until 11 pm tonight, possibly later too. E. Majorana”

But shortly after, he sent a telegram saying he had canceled his plans. He’d bought a ticket from Palermo to Naples, and then was never seen or heard from again.

Some believe he escaped to Argentina, others believe he committed suicide, others believe he was killed or kidnapped due to the possibility of his participation in building an atomic bomb, others believe he simply left to become a beggar or a monk. But no solid proof has ever been found of what happened to Ettore Majorana.