Ancient Aliens Season 16, Episode 3, "The Galactic Keyhole," explores the recurrence of keyhole-shaped structures in ancient architecture, such as Japan’s Daisen Kofun and Sardinia’s Santa Cristina Well, suggesting they are extraterrestrial blueprints. Theorists propose these sites and artifacts, including the Egyptian Menat, represent a "galactic key" left by extraterrestrial teachers to signal beings in the sky. Read the full transcript at Fandom . The Galactic Keyhole (Se16 Ep3)/Transcript