There is a mysterious and loud radio signal known as 'the space roar' that has yet to be explained.
15
In 1958, a nuclear bomb was lost somewhere along the swampy coast of Georgia. Its whereabouts remain a mystery to this day.
29
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
A waterfall known as The Devil's Kettle empties water into a hole and nobody knows where it ends up!
18