What on Earth?

A single image sparks a global hunt. From a wrecked plane tied to a Colombian drug lord to clues of a vampire burial in Romania and a mysterious city hidden beneath the sea.

The 'Nazi Gold Train' remains one of WWII's greatest mysteries, the legend of a hidden train packed with stolen riches, buried in south-west Poland as the war drew to a close. (S4, ep 2)

Strange markings could be a coded message with a plot to overthrow the Queen of England and a lake with healing powers holds clues to life on Mars. (S4, ep 3)

A ghost town covered in a strange, white power emerges from a lake in Argentina and a declassified CIA image uncovers a bizarre, giant Soviet weapon. (S4, ep 4)

When a man-made island mysteriously appears off the US coast, grisly new evidence points to secret government experiments into psycho-chemical warfare. (S4, ep 5)

Embark on an eye-opening journey as experts investigate the startling mysteries captured by satellites orbiting the Earth: from hidden worlds to unexplainable natural phenomena. (S4, ep 6)

When a labyrinth is discovered on an island once home to an ancient Greek civilization, experts investigate if it was the home of the Minotaur. (S4, ep 7)

Embark on an eye-opening journey as experts investigate the startling mysteries captured by satellites orbiting the Earth: from hidden worlds to unexplainable natural phenomena. (S4, ep 8)

When a mysterious circular stone structure is discovered in Scotland, experts investigate whether it's the fabled Round Table of King Arthur. (S4, ep 9)

Embark on an eye-opening journey as experts investigate the startling mysteries captured by satellites orbiting the Earth: from hidden worlds to unexplainable natural phenomena. (S4, ep 10)

Embark on an eye-opening journey as experts investigate the startling mysteries captured by satellites orbiting the Earth: from hidden worlds to unexplainable natural phenomena. (S4, ep 11)

Embark on an eye-opening journey as experts investigate the startling mysteries captured by satellites orbiting the Earth: from hidden worlds to unexplainable natural phenomena. (S4, ep 12)

Embark on an eye-opening journey as experts investigate the startling mysteries captured by satellites orbiting the Earth: from hidden worlds to unexplainable natural phenomena. (S4, ep 13)

Embark on an eye-opening journey as experts investigate the startling mysteries captured by satellites orbiting the Earth: from hidden worlds to unexplainable natural phenomena. (S4, ep 14)

A mysterious structure in Africa that resembles Stonehenge is said to be the resting place of a mythical giant. (S4, ep 15)

Embark on an eye-opening journey as experts investigate the startling mysteries captured by satellites orbiting the Earth: from hidden worlds to unexplainable natural phenomena. (S4, ep 16)

Embark on an eye-opening journey as experts investigate the startling mysteries captured by satellites orbiting the Earth: from hidden worlds to unexplainable natural phenomena. (S4, ep 17)

A strange mountain in Egypt sparks an investigation into Cleopatra's gems and the tomb of Alexander the Great. (S4, ep 18)

Embark on an eye-opening journey as experts investigate the startling mysteries captured by satellites orbiting the Earth: from hidden worlds to unexplainable natural phenomena. (S4, ep 19)

Embark on an eye-opening journey as experts investigate the startling mysteries captured by satellites orbiting the Earth: from hidden worlds to unexplainable natural phenomena. (S4, ep 20)