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Theorists speculate about the existence of black holes on Earth, which may explain strange disappearances and other inexplicable phenomena.

Researchers study giant ancient drawings found etched into the desert floor, which may be a part of an ancient alien code.

Experts in the extra-terrestrial examine the Inca ruin and its mysteriously intricate carved blocks.

Explore the most devastating disasters ever documented that may have an otherworldly connection, from a flying monster to a deadly virus.

From glyphs in the Peruvian desert to spiral petroglyphs embedded with advanced maths, explore some of the world's most intriguing symbols and codes.

From a meeting in Texas that left onlookers with mysterious injuries to strange cattle mutilations, discover history's terrifying encounters.

The Top Ten Hidden Alien Bases: Discover 10 locations around the world that just might be hiding alien bases, from a cavern beneath the ice in Antarctica to a Chinese lake.

Could Area 51's notoriety act as a cover up to much bigger, top-secret extraterrestrial experiments taking place at multiple locations.

Oak Island treasure hunter Marty Lagina and Ancient Astronaut theorist Giorgio A. Tsoukalos explore the ancient ruins of Sardinia, Italy.

Five years after John F Kennedy is killed by gunshot, his brother Robert meets the same fate - and the clues are riddled with inconsistencies.

What will humans find when reaching other planets? And just how dangerous might it be.

When humanity vanishes, the vast infrastructure underground, from subways and pipelines in the United States, begins to unravel.

Could Area 51's notoriety act as a cover up to much bigger, top-secret extraterrestrial experiments taking place at multiple locations.

Oak Island treasure hunter Marty Lagina and Ancient Astronaut theorist Giorgio A. Tsoukalos explore the ancient ruins of Sardinia, Italy.

60 years on, Tony's close encounter has become an obsession. Meanwhile, pilot David presents photographic evidence of the UFO he almost crashed into whilst flying near area 51.

Adam, Gwen and Julie recall personal encounters with UFOs, before experts' theories are put in doubt when we learn that each individual has time missing from their encounters.

In 1996, one of the worst disasters in American history left 230 people dead and questions unanswered in a tragedy that changed the aviation industry forever.

Explore the top theories behind what happened to the treasure looted by the Japanese during World War II.

In 1990, thieves stole half a billion dollars in masterpieces from the Isabella Stewart Gardner Museum. Who orchestrated the infamous heist and why.

Troy answers an urgent call from his long time friend and fellow swamper, Daniel Edgar, who has discovered a mysterious threat to the alligator population.

Could some of our ancient texts and structures be home to secret messages left by alien ancestors? If so, what can we learn from them.

Each episode explores three artefacts drawn from museum collections, private archives and Bruce's own unrivalled holdings.

Each episode explores three artefacts drawn from museum collections, private archives and Bruce's own unrivalled holdings.

Sucked Up by a Tornado, Elevators Gone Wrong, Motorcycle vs. Flood and the Indian Ocean Tsunami of 200: A woman survives being sucked into a tornado.

The Hindenburg Disaster, Pilot's Ejection Fail, When Trees Attack & Stuck In A Cave: A pilot activates his ejector seat at the last second during a rocky landing.

Could Area 51's notoriety act as a cover up to much bigger, top-secret extraterrestrial experiments taking place at multiple locations.