The oldest nucleus of Elaiussa Sebaste was built on the promontory overlooking the city's two ports. The thin isthmus was always the startegic nod of the city, and through its control it was possible to rule the land and sea circulation of men and goods that allowed Elaiussa to obtain ease and prosperity. It's not so surprising then that the defensive structures in polygonal masonry are among the city's oldest elements, since their early dating between the II and the I century before Christ.
During the II century AD some sectors of the peninsula were monumentalized, with the extension of the defensive structures in opus quadratun, that comprised rectangular and semicircular towers. A great semicircular bastion was built near the promontory's SW angle, where two rectangular towers protected the monumental gate opened on the road connecting the peninsula with the mainland. In front of the North Port was built a portico, embellished with column's of grey marble. The portico's inner wall, in opus quadratum, has a concave course. Six doors open on this wall; the second last of them is the widest, framed with pillars crowned by corinthian capitals with smooth leaves. An inscription dedicated to Septimius Severus and Caracalla allowed the dating of the building's completion or reconstruction in the reign of the first of the two emperors named in the epigraph.