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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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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The Platypus used to be considered a myth like Bigfoot and the Yeti.
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There are pictures of Knights fighting Snails in old Medieval manuscripts - and nobody knows why.
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