Alexandria began as Alexander the Great's vision in 331 BC: a city where all the world's knowledge could be gathered in one place. Bettany Hughes traces how that ambition built the Great Library and the lighthouse of Pharos, structures sophisticated enough to make the city a magnet for scholars and a hub for Mediterranean trade. She walks through the intricate water system engineers built to keep a desert port alive, and follows the roster of figures who passed through the city's political and intellectual life, including Julius Caesar, Cleopatra, the mathematician Euclid, Archimedes, Eratosthenes, and the philosopher Hypatia. Much of ancient Alexandria now sits underwater or beneath the modern city, and Hughes draws on recent excavation finds to reconstruct what the harbor, the library, and the streets actually looked like before the city's decline in the fourth and fifth centuries AD. The film treats Alexandria as an experiment in concentrating knowledge and wealth in a single place, and asks what that experiment cost the city when it finally collapsed.