Caesaraugusta — the Roman name for Zaragoza — was founded by Augustus in 14 BC as a major colonial city on the Ebro. The city's Roman remains are scattered across the old town, but the Roman Theatre museum (Museo del Teatro de Caesaraugusta) is the most impressive: the foundations and lower seating tiers of a theatre that could hold around 6,000 spectators, preserved beneath the street level and viewable from elevated walkways through a modern museum building.
The museum on Calle San Jorge presents the excavations clearly and includes recovered artefacts from the site. Combined tickets are available with Zaragoza's other Roman sites — the Forum, the Baths, and the Port — making a half-day circuit of Roman Caesaraugusta an excellent itinerary. The level of preservation is exceptional given that the city has been continuously inhabited for 2,000 years.