The 10 Greatest Unsolved Mysteries

The last hundred years have borne witness to humankind's extraordinary technological advancements. Man has walked on the moon, ventured deeper into the oceans than ever before and even uncovered the building blocks of life, DNA.

But even with our inexorable progress as a species there are still mysteries and enigmas the solutions to which elude us. Here is a selection of 10 of the most puzzling mysteries in history.