Underwater Worlds: Ruins in Peru support legends of a sunken UFO base and Indian texts talk of water worlds populated by aliens. Could aquatic cities prove that aliens visited? (S2, ep 10)

The Vanishings: Experts explore the disappearance of civilisations throughout time and across the globe. Could clues left in their wake point to an otherwordly explanation? (S7, ep 9)

The Shamans: Throughout history, spiritual leaders known as shamans have healed, protected and advised. Could they really be in contact with extraterrestrial realms? (S6, ep 9)

Alien Operations: Experts investigate reports of bird-like figures that practised advanced medical science in ancient times. Could they have been extra-terrestrial? (S5, ep 9)

Aliens And Cover-ups: In 1980, a man received a code after touching an alleged spaceship. After the sequence was translated, he was told never to speak of the incident again. (S4, ep 9)

Aliens And Deadly Weapons: From gunpowder to missiles, were these lethal weapons the product of human innovation, or were they created with help from another, otherworldly source?

Unexplained Structures: Could aliens have helped humans build huge ancient structures? Experts ask whether standing stones in France, were a GPS system for ancient spacecraft. (S2, ep 9)

Circles from the Sky: Crop circles are a global phenomenon, with 10,000 seen worldwide. But are these strange patterns simply a hoax or could they be proof of UFO activity? (S8, ep 8)

The Great Flood: Experts find evidence suggesting that ancient aliens saved humanity from great floods sent by the gods. Can we rely on extra-terrestrials to save us again? (S7, ep 8)

Aliens And The Red Planet: Experts question what probes on Mars may have found over the past 40 years. Could NASA be hiding proof of life on the Red Planet from the public? (S6, ep 8)