Since 1982, a radio frequency emanating from Russia has been broadcasting a buzzer-like sound and, periodically, an unknown voice reads orders, names, and numbers. No one knows where exactly it is coming from or what it means.
13
There's a mysterious dwarf planet between Mars and Jupiter called 'Ceres' which has never been visited by spacecraft or photographed in detail, however, Earth-bound telescopes reveal a large bright shining spot on the surface of this planet, the origin and nature of which are unknown.
5
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 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
There is a mysterious and loud radio signal known as 'the space roar' that has yet to be explained.
15