The single arched passageway of the lower level is 6.5m wide and was supported by pilasters crowned with Corinthian capitals. Similar, but taller, pilasters flank the outer corners of the lower level. The space between the outer pilasters and the arched opening was filled in with squared stones with drafted edges to emphasize the design.[2] On either side of the central passageway was a Corinthian column on a rectangular, raised base projecting from the center of the wall.