This chapter starts by considering notions of architectural beauty in Flavian Rome. It explores the aesthetic criteria attested by Vitruvius, their roots in Greek Hellenistic theory, and their legacy for later architectural aesthetics, but also highlights new aesthetic principles such as the use of polychromatic marbles and their influence on perceptions of buildings, especially in the eastern empire. The writings of Tacitus and the younger Pliny reflect divergent views on architecture, while the works of Lucian offer a guide to the aesthetic experience of public buildings in the East. A contrast is observed between the notion of beauty (pulchritudo), involving grandeur and spaciousness, and the more refined aesthetic of venustas, associated with small-scale works such as fountain buildings, baths, shrines, and tombs, which emphasized the attainment of beauty through precious marbles such as alabaster and virtuoso forms, particularly spirally fluted columns and conches. This second idea became commoner in the Severan period, encouraging symbolic readings of building materials which would become characteristic of late antiquity and Byzantium.