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?