There is a mysterious and loud radio signal known as 'the space roar' that has yet to be explained.
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A waterfall known as The Devil's Kettle empties water into a hole and nobody knows where it ends up!
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The Platypus used to be considered a myth like Bigfoot and the Yeti.
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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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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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