Verbonia is a fictional Roman town in Gaul, built to illustrate how a real Roman city actually worked, and David Macaulay uses it as the spine for a film that mixes animation with live-action visits to Pompeii, Herculaneum, Ostia, Nimes, Orange, and Rome itself. The animated sections follow Verbonia's planning and growth, and its later strain as conquerors and conquered try to coexist within the same walls and streets. The live footage grounds that story in surviving structures: amphitheaters, aqueducts, bathhouses, and the layout of the Colosseum, treated as evidence for how the fictional town's engineering would have functioned in practice. Macaulay, working from his own illustrated book, keeps returning to ordinary mechanics rather than spectacle alone, water supply, road grids, public buildings, the systems that let tens of thousands of people live in one place. The film's case is that a single invented city, built carefully enough, can explain more about Roman urban life than a tour of ruins alone.