There is an island near Italy that was the site of wars, a dumping ground for plague victims, and an insane asylum. It's considered so dangerously haunted that the Italian government does not allow public access.
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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 are pictures of Knights fighting Snails in old Medieval manuscripts - and nobody knows why.
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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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