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.
16
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.
19
There are pictures of Knights fighting Snails in old Medieval manuscripts - and nobody knows why.
23
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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