This gate provides access to the west of the city and it is the most impressive among the seven gates of Pompeii. The name derives from the fact that the exit road led to the sea. The layout with a barrel vault made of concrete, that is a mixture of mortar and stones, dates back to the Silla colony (80 BC).

The gate has two fornix, the main one being higher, intended for the passage of horses and pack animals; the smaller one, intended for pedestrian passage. The city wall that can be seen today, already in place in the 6th century BC, is over 3200 m long: it consists of a double wall with a walkway, protected inside by an embankment. Twelve towers, more on the north side where the flat terrain made Pompeii more vulnerable, guaranteed defence. The definitive entrance of the city within the Roman orbit decreased the importance of the walls, sometimes re-used and destroyed to make place to homes.

Date of excavation: 1862-1863.