In this retrospective countdown episode, Giorgio Tsoukalos ranks his top ten "alien artifacts" that he believes suggest extraterrestrial visitation in antiquity. The list includes the Mitchell-Hedges crystal skull, discovered in 1924 at Lubaantun, Belize, which Tsoukalos claims was analyzed by Hewlett-Packard and found to be carved against the crystal's natural axis—something that should cause quartz to shatter without modern power tools. Ancient astronaut theorists point to legends across cultures describing exactly thirteen crystal skulls of otherworldly origin scattered globally, and suggest these objects may store advanced information in the crystal matrix, just as modern technology uses quartz for data storage. The episode also features the Saqqara Bird from Egypt, a wooden object theorists describe as resembling a modern glider rather than a simple bird figurine.
Mainstream archaeology tells a different story about these objects. The British Museum and Smithsonian have tested multiple crystal skulls using electron microscopy, finding tool marks consistent with 19th-century jeweler's equipment—not ancient technology. The Mitchell-Hedges skull's provenance is particularly suspect, with no documentation of its 1924 discovery and evidence suggesting Frederick Mitchell-Hedges purchased it at a Sotheby's auction in 1943. Still, the episode raises genuinely intriguing questions about how ancient craftspeople achieved remarkable precision with available tools, making it engaging for anyone curious about the technical capabilities of past civilizations, even if the extraterrestrial explanation requires extraordinary leaps beyond the archaeological evidence.