Ancient Aliens - Season 21

Ancient Aliens is counting down ten of history's most astonishing discoveries – breakthroughs that challenge traditional beliefs about human history. From a lost city hidden in the Andes to mysterious metal spheres that are not of this world and a sunken city that was said to be the home of the gods, could these discoveries provide proof of extraterrestrial contact?

Ancient Aliens is counting down the world's top ten most mysterious monoliths, from a 500-ton stone believed to represent an ancient UFO, to giant statues said to have been created with advanced technology, and ornate pillars that depict otherworldly visitors. Could these extraordinary standing stones provide evidence of extraterrestrial visitation?

Ancient Aliens is counting down ten of the most compelling UFO crashes that have been reported across the globe. From an acorn-shaped object that crashed in the woods of rural Pennsylvania, to a mysterious craft that washed ashore in Japan, and an earth-shaking impact in Britain that defies explanation, are these mysterious events proof that our planet has been visited by extraterrestrials?

Ancient Aliens is counting down ten of the most astonishing--and unexplainable--technologies in history. From mysterious golden orbs discovered in Mexico, to a sacred wooden box that could communicate with the heavens, and an ancient tomb that is said to depict an astronaut, might these sensational artifacts be evidence of otherworldly contact?

Ancient Aliens is counting down ten of history's most compelling -- and covert -- projects that study the UFO phenomenon. From clandestine government organizations to agents that silence UFO witnesses and secret programs to reverse-engineer alien technology, are these mysterious projects evidence of contact with extraterrestrials?

Ancient Aliens is counting down ten mysterious mountains that are notorious for otherworldly phenomena.  From a summit in Sri Lanka that is said to be a portal to other worlds, a volcano in Washington that was at the center of a famous UFO sighting, and a mesa in New Mexico believed to contain an alien base, could these strange peaks provide evidence of extraterrestrial contact?

The Aztecs built one of the world's most powerful and feared empires, and they claimed that they were guided by a pantheon of more than a thousand gods who came to Earth from different parts of the universe. Could the incredible story of their rise to power – and their sudden demise – reveal a history of extraterrestrial intervention in Mesoamerica?

Across the globe, reports of mysterious glowing orbs are on the rise. Their movements frequently defy the laws of physics, and now they are even being reported near military bases, ships, and nuclear weapon facilities. Do they represent a non-human intelligence? And if so, why are they here?