There are pictures of Knights fighting Snails in old Medieval manuscripts - and nobody knows why.
23
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 600 year old 240 paged book called the Voynich Manuscript, that’s written language is still completely unknown today.
15
A waterfall known as The Devil's Kettle empties water into a hole and nobody knows where it ends up!
18
There is a mysterious and loud radio signal known as 'the space roar' that has yet to be explained.
15
The Platypus used to be considered a myth like Bigfoot and the Yeti.
18