Caesaraugusta was founded by Augustus around 14 BCE at the site of the Iberian settlement of Salduie on the Ebro River. Veterans of Roman legions received land in the new colony, whose name uniquely incorporated the emperor’s full title. Its river crossing and access to roads made it an administrative, commercial, and transport center in the middle Ebro valley. A planned street grid, walls, port, water supply, sewers, baths, forum, and entertainment buildings established the civic infrastructure of a Roman provincial city.

The forum visible beneath today’s Plaza de la Seo largely dates from the reign of Tiberius. Porticoes, shops, administrative rooms, and a great sewer supported religious ceremony, government, law, and trade. Its position near the Ebro linked civic business with the river port. Magistrates, priests, merchants, clients, workers, and residents crossed the precinct daily. The surviving foundations and drains may appear utilitarian, but marble facing, columns, sculpture, inscriptions, and painted surfaces would have made the original center an imposing expression of Roman authority.

Construction of the theater began under Tiberius and continued into the mid-first century. Unlike theaters cut into a hillside, its seating rose on a system of radial walls, vaults, and galleries. With capacity for thousands, it hosted drama, music, civic ceremonies, and public spectacle. Seating mapped social rank, while sponsorship advertised elite generosity. The building declined during the third century and was systematically stripped of valuable material. Houses and streets later occupied the site, preserving the theater’s foundations beneath successive Islamic, medieval Christian, and modern neighborhoods.

Urban archaeology exposed the forum between 1988 and 1991 and the theater after its discovery in 1972. Excavation required removing or integrating later structures and conserving remains below a living city. Zaragoza developed separate site museums for the forum, theater, river port, and public baths, creating a route through Roman infrastructure rather than assembling everything in one detached collection. Modern roofs and walkways protect walls and allow visitors to understand ancient levels far below present streets.

The municipal museums now present complementary parts of Caesaraugusta. At the forum, foundations, sewers, and objects explain administration and commerce; at the theater, the cavea, orchestra, stage foundations, and recovered decoration communicate entertainment and urban transformation. Neither site is a complete monument, and their separation reflects the modern city covering the ancient one. Together they show how a colony founded for veterans became a complex community, how public architecture organized social life, and how archaeology can reconnect buried fragments without erasing the later history built above them.