Hannah decodes the Parthenon's geometry, sails the Aegean with ancient tools, and attends a flour-throwing festival that blends ancient myth with modern identity.

Hannah Fry visits Iceland to uncover the secrets behind its success. She meets scientists predicting lava flows, sees how geothermal power fuels an algae farm, explores Icelandic DNA and rides horseback through ancient Viking landscapes - all to reveal how a tiny, isolated island, shaped by geological extremes, is thriving against the odds.