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
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
A waterfall known as The Devil's Kettle empties water into a hole and nobody knows where it ends up!
18