Even a casual examination of this arch, with a few of the many preserved Roman triumphal arches in mind, reveals the significant design variation between the two structures. The number of arched passageways of the lower level of Roman triumphal arches was variable as was the presence of a secondary passageway along the long axis of the structure; as a dipylon arch with a single passageway, the lower level of the Arch of Hadrian falls within the gamut of the architectural genre. Roman triumphal arches, however, typically have a massive, solid attic (upper level), often filled with a dedicatory inscription and sculptural decoration. In addition, Roman arches typically supported major stone or bronze statuary, often including a quadriga (four-horse chariot) or similar at top center. As Willers notes, the design of the Arch of Hadrian has a very refined upper level that does not allow the mounting of major decoration on top of the attic.