Follow a team of international scientists documenting an archaeological sensation: the exploration of royal tombs beneath the ancient Mexican city of Teotihuacan. Despite many decades of research, not much is known about this long-lost society. When archaeologists discover evidence of a sacrificial chamber beneath the famous Pyramid of the Feathered Serpent, they find the clues that may finally tell us who these mysterious people were. 2016. Running time, 60 minutes.