There are pictures of Knights fighting Snails in old Medieval manuscripts - and nobody knows why.
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There is a 600 year old 240 paged book called the Voynich Manuscript, that’s written language is still completely unknown today.
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In 1958, a nuclear bomb was lost somewhere along the swampy coast of Georgia. Its whereabouts remain a mystery to this day.
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Scientists lit a cave of natural gas on fire in 1971 expecting it to only burn for a few days; it still burns to this day. It has been nicknamed "The Door to Hell".
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The exact cause of death and burial site of Genghis Khan is unknown, because all of the 2000 funeral guests and 800 soldiers were killed in order to preserve the secret.
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In 1518, a "dancing plague" struck Strasbourg, Alsace, whereby hundreds of people danced fervently in the streets over the period of a month. Some suffered heart attacks or strokes, and many others died from sheer exhaustion. It remains unexplained.
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There's a mysterious dwarf planet between Mars and Jupiter called 'Ceres' which has never been visited by spacecraft or photographed in detail, however, Earth-bound telescopes reveal a large bright shining spot on the surface of this planet, the origin and nature of which are unknown.
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