1. Roman Britain - The Work of Giants Crumbled

Roman Britain transformed from a frontier outpost into a glittering metropolis before suffering a protracted, multi-century collapse. The province’s fatal flaw—the "British mistake"—involved governors repeatedly stripping the island of its military garrison to launch failed bids for the imperial throne, leaving the region vulnerable to internal rebellion and external raids. Coordinated attacks like the Great Barbarian Conspiracy of 367 AD shattered Roman confidence, while economic decline manifested in abandoned infrastructure, plummeting iron production, and the cessation of trade. By the time Emperor Honorius formally ended the Roman presence in 410 AD, the province had already descended into anarchy. The subsequent abandonment of cities like London and York, coupled with the repurposing of Roman masonry for medieval structures, left behind a landscape of ghosts that defined the British perception of a lost, legendary age.