The Porta Marina or Sea Gate belongs to the city walls of the first century BC. It received its (modern) name from the nearby beach. The gate was excavated in 1938-1942.
Plan of the Porta Marina. SO I, fig. 28.
The gate consists of a single room, made of large tufa blocks. On the south side are grooves for the wooden doors. Pivot-holes have also been preserved. On either side of the gate is a square tower, with sides of 4.40 to 4.50 metres. In the first century AD the gate was razed to the ground. In the years 210-235 AD the Bar of Alexander and Helix (IV,VII,4) was built on the east side. As a replacement an arch decorated with marble was built, five metres to the south. Between the gate and the arch a mediaeval lime-kiln was found.