Ancient Aliens - Season 17

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.

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.

Mount Shasta in northern California is known as a hotbed of strange events, from Big Foot sightings to UFO encounters to hikers vanishing without a trace. Could the mountain's unique geology and placement on Earth be attracting beings from other worlds?

Scientists now know that seven human-like species lived alongside Homo sapiens for thousands of years. But why is it that only humans survived? Is it possible that we were the product of extraterrestrial experimentation?

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.