Roman London developed beside a Thames crossing soon after the conquest of Britain in 43 CE. Merchants, soldiers, administrators, and migrants turned Londinium into a provincial capital with a port, forum, baths, temples, and extensive suburbs. Two surviving monuments illustrate different aspects of its public life: the amphitheatre beneath Guildhall and the defensive wall whose fragments remain around the City. They were built in separate campaigns, and their histories should not be compressed into a single foundation date or one construction project.

The first amphitheatre was built in timber around 70 CE and later reconstructed in more durable materials. Its oval arena accommodated gladiatorial contests, animal displays, punishment, and ceremonial gatherings before several thousand spectators. Entrances and service chambers controlled movement between the arena and surrounding streets. Games expressed civic ambition and Roman social hierarchy, with privileged spectators occupying better positions. The building also depended on a less visible world of animal handlers, attendants, enslaved workers, suppliers, and performers whose experiences rarely appear in surviving written accounts.

Around 200, builders enclosed the landward city in a substantial stone wall using Kentish ragstone, mortar, and distinctive horizontal courses of red tile. The structure marked civic status, regulated access, and provided defense. A riverside circuit and projecting bastions were added later as conditions changed. Roads passed through controlled gateways, and the wall incorporated the earlier military fort near Cripplegate. Its construction required enormous quantities of quarried material and river transport, demonstrating the resources available to the prosperous provincial city.

After Roman government ended, the amphitheatre fell out of use and disappeared beneath later occupation. The wall survived more visibly, influencing the medieval city's boundaries and street names. Repaired defenses, gates, houses, and religious buildings incorporated its masonry. Modern growth destroyed long stretches, but antiquarian recording, excavation, and wartime redevelopment exposed surviving sections. In 1988 archaeologists found the amphitheatre during work for Guildhall Art Gallery, resolving a longstanding question about the location of London's principal Roman arena.

Preserved remains beneath the gallery now reveal an entrance and adjacent structures, while paving in Guildhall Yard traces the arena's outline above. Wall fragments at Tower Hill, Cooper's Row, the Barbican, and elsewhere connect Roman construction with medieval additions. Conservation must address moisture, pollution, development, and the difficulty of explaining buried structures inside a living financial district. Together these monuments show how public spectacle and urban boundaries shaped Londinium, then continued to influence London through survival, reuse, disappearance, and archaeological recovery over almost two thousand years.