This dissertation is the first comprehensive study of columbarium tombs in early Imperial Rome. I use an interdisciplinary approach to analyze their design and usage from the perspective of commemoration. Columbaria were subterranean chamber tombs, housing up to several hundred niches with urns for cremation burials. They were almost exclusively constructed in Rome and its environs in the Julio-Claudian period from ca. 30 B.C. to ca. 50 A.C. for the burial of non-elite individuals, many of whom were slaves and freedmen. These innovative tombs have never been studied as a phenomenon and as a consequence, they have been dismissed as inexpensive mass graves. This study crosses traditional boundaries of classical scholarship analyzing funerary architecture, art, and inscriptions in concert. Using this approach, I argue that the visual appearance of burial spots and the texts of funerary inscriptions are "commemorative languages" revealing how columbaria negotiated between individuals and groups. Their underground location produced a wholly non-elite environment, in which commemoration was non-competitive. The similarity and strict arrangement of burial niches visually emphasized the equity of the tombs' occupants, a commemorative strategy that broke with existing funerary traditions. But a few generations after columbaria first appeared, some users started to distinguish their niches visually. This evolvement is also evidenced in the numerous funerary inscriptions columbaria have produced, in which the deceased are described with increasing detail over time. The return to more competitive commemoration parallels the development of Roman funerary art in the first century A.C., for example in the use of costly funerary altars and urns. I conclude that the habit to bury collectively reflects a social process, the social integration of slaves and former slaves who increasingly occupied central positions in municipal and Imperial administrations. At the same time, new legislation distinguished them from freeborn citizens, a segregation that was reflected in funerary architecture. The new tombs set them apart from other inhabitants of Rome reflecting a growing group identity. Subsequently, this identity slowly faded as it became more important for some occupants to commemorate their individual achievements than to emphasize their belonging to the burial collective.