 The design of this central aediculum-like, niche of the upper level is similar to the architecture of the "scaenae frons" (façade of ancient stage buildings) and highly evocative of the representations of aedicula in wall painting of the 2nd Pompeian style.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.