Machu Picchu is fascinating to archaeologists and historians because it is not documented in any of the ancient chronicles of the Spanish conquistadors.

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?

Some people in Mount Shasta believe that a lost continent called Lemuria is hidden beneath the mountain, along with its capital crystalline city, Telos.

Numerous experiments which were performed on human test subjects in the World.

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?

Ancient Aliens has 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.