Several stories tell of people who have disappeared under rather mysterious circumstances and although they've left behind clues, no one has been able to determine what ultimately happened to them.
Some of them had gone in search of legendary treasures and it's believed that their ambition for getting rich quick had ultimately cost them their lives.
Whether their disappearance was the result of a series of unfortunate events or it was all a cleverly devised scheme that managed to mislead even the best detectives, you decide.
The following are the stories of individuals who disappeared decades ago and whether they were killed remains an enigma.
The fate of adventurer Percy Fawcett is the subject of a number of documentary films. In 1925, he and his 21-year-old son named Jack, started on an expedition in South America in search of the legendary El Dorado. On May 29, Fawcett vanished, leaving behind only his compass, which was found years later and no one knows what exactly happened to the explorer.
Called the "Prince of Explorers" because he returned home safe and sound after many dangerous expeditions, his good luck took a turn for the worse in 1848, when he vanished without a trace during an expedition in Australia. A number of theories cropped up, including starvation, a conflict within the group and shark attacks, although the only sign left after his disappearance was a plate with the letter "L".
Michael Rockefeller was the son of millionaire Nelson Rockefeller and an avid archaeology admirer. But after one particular expedition in search of antiquities, he never returned. Some speculate that he was eaten by cannibals but evidence was insufficient to confirm this.
19-year-old Tara Calico was a college student in New Mexico, when she disappeared while riding her bicycle. Initially, only pieces of her Walkman were found, 18.5 mi (30 km) from the spot where she was last seen. After years of searching, police found only a photo showing Tara, tied up, with a boy next to her, who had disappeared several months prior to Tara.
Writer Ambrose Bierce vanished mysteriously in 1913 en route to Mexico. Several theories have been proposed about his disappearance, among which are that he was attacked by a group of Mexican bandits or that he was locked up in a madhouse. The last letter Ambrose sent to his sister raises suspicions that he could have committed suicide.