Giorgio A. Tsoukalos, David Childress and William Henry examine a recently discovered lost city in Peru that has upended the historical timeline of South America, revealing that civilization emerged thousands of years earlier than previously thought.

Ancient Aliens is counting down the world's top ten most mysterious sites, from the towering Moai statues of Easter Island to the enormous megalithic blocks of Stonehenge to the precision cut stones of Puma Punku. Could these extraordinary places provide evidence of extraterrestrial visitation?

Ancient Aliens is counting down the world's top ten alien cover-ups, from the famous Roswell Incident to a secret military base rumored to be housing ET technology to recently released UFO videos captured by cameras on Navy fighter jets. Has there been a massive cover-up regarding the truth about an extraterrestrial presence on Earth?

Examining the unique geology and location of Mount Shasta in northern California, to determine why it is known as a hotbed of strange events, from Bigfoot sightings to UFO encounters to hikers vanishing without a trace.

We're counting down the world's top ten alien encounters, from the first reported abduction event to mass UFO sightings over New York's Hudson Valley to an incident in ancient Rome that changed the course of human history. Could these incredible accounts be actual encounters with visitors from the stars?

An ancient figurine of a modern-day airplane. A primitive statue of a man in a spacesuit. Mysterious crystal skulls whose origins are entirely unknown. For more than a decade on Ancient Aliens, we've traveled the globe and investigated strange objects found on every continent on Earth. We're counting down the top ten alien artifacts. Objects that could provide evidence that extraterrestrials once walked among us.