At his own expense Augustus built his own aqueduct, known as Aqua Iulia, for Capua, located in today's Campania region of southern Italy, which was in Roman times, one of the most important civitas of the empire. The course of this aqueduct and of its likely branches, destined for two small towns, Saticula and Calatia, is hypothesized, in part based on the re-use in the seventeenth century of about 8 miles (i.e. 11.8 km) of the ancient aqueduct for another water supply that served Naples, namely the Carmignano aqueduct. The subsequent transformation in the eighteenth century in a new water supply along a new route at a higher altitude is described. This third water supply served the Bourbon royal palace of Caserta, a magnificent construction built in the same period. In summary, the historical evolution of the Augustan aqueduct of Capua is discussed in the context of the communities served and in the context of the organization and history of the territory supplied, demonstrating the richness of information that may be obtained by an integrated study of the transformation, over time, of this important water infrastructure.