The legend of secret tunnels beneath the White House gained prominence during Franklin D. Roosevelt's presidency, with claims that he used them to move around the city unseen.

The Illuminati, a purported secret society, has been frequently mentioned in conspiracy theories surrounding the assassination of John F. Kennedy.

The legend of the Lost City of Atlantis is often associated with the biblical account of the Great Flood, with claims that Atlantis was a technologically advanced civilization that was destroyed by a cataclysmic flood.

Area 51, a remote military base in Nevada, has been the subject of numerous conspiracy theories, including claims that it is a site for studying extraterrestrial life and technology.

The legend of the Holy Grail, a sacred cup said to have been used by Jesus Christ at the Last Supper, is often linked to King Arthur and the Knights of the Round Table.

The Bilderberg Group, a private annual conference of influential people from industry, finance, academia, and politics, has been the subject of conspiracy theories claiming that it is a secretive organization working towards a global agenda.

The legend of the Curse of the Pharaohs, which claims that misfortune and death befall those who disturb ancient Egyptian tombs, gained prominence after the opening of King Tutankhamun's tomb in 1922.

Project MKUltra, a covert CIA program that experimented with mind control and psychological warfare techniques during the Cold War, has been the subject of numerous conspiracy theories.

The legend of the Spear of Destiny, a weapon said to have been used by Jesus Christ during the crucifixion, is often linked to Adolf Hitler and the Nazi regime.

The Illuminati, a purported secret society, has been frequently mentioned in conspiracy theories surrounding the death of Princess Diana.

The legend of the Bermuda Triangle, a region of the Atlantic Ocean where ships and aircraft are said to mysteriously disappear, is often associated with the disappearance of Amelia Earhart in 1937.

Project HAARP, a high-frequency active auroral research program, has been the subject of conspiracy theories claiming that it is a secret government project capable of manipulating the weather and climate.

The legend of the Fountain of Youth, a mythical spring said to restore youth and vitality, is often linked to Spanish explorer Juan Ponce de León.

The Illuminati, a purported secret society, has been frequently mentioned in conspiracy theories surrounding the assassination of Abraham Lincoln.

The legend of the Loch Ness Monster, a cryptid said to inhabit Loch Ness in Scotland, gained prominence after the sinking of the USS Cyclops in 1918, with claims that the monster may have been responsible for the ship's disappearance.