Built of huge blocks of cornelian, it measures 32 m in length and 3.25 m in width at the top of the arch. This monument is emblematic of the old Roman “ municipium” of Suillum (governed by the two “duoviri”, together with the “quattuoviri” college of magistrates), as well as symbolizing the ancient and deep-rooted connection between the Tyrrhenian and the Adriatic Sea. The famous staging-post on the Via Flaminia, Helvillum, could be found within the territory of Suillum. From here, a branch road crossed the mountains and led on to Ancona. It remained in use for many centuries, until the beginning of the 1900’s and was known as the “Postiglione” (Postillion).