S1, E1: One of the most compelling arguments for the Ancient Astronaut theory is the remarkable engineering evident in the construction of ancient megalithic sites worldwide. Join experts Giorgio Tsoukalos, William Henry, and Jason Martell as they embark on a global investigation, revisiting the series archives of Ancient Aliens to explore the most enigmatic archaeological sites, including Giza, Puma Punku, Nan Madol, Baalbek, and others.