During the Roman period, the city had enjoyed economic prosperity based mainly on the production of garum and salsamenta and their marketing.

The district of the salting factories, discovered in Neapolis, is made up of independent units, around which dwellings and shops linked to the production facilities were set up. The first phase of the salting plant was built in the 60's - 80's AD and the second phase was built at the end of the 2nd century AD. The demise of this factory began towards the end of the 3rd century AD. The abandonment of this factory began towards the end of the 3rd century AD and was completed in the last third of the 4th century AD.

By its salting factories and the considerable number of recognized vats on the site Neapolis is one of the largest centres of garum production in the Roman world.

Underwater prospecting in Neapolis revealed the presence of submerged structures. The engulfment of part of the city is the catastrophic consequence of an earthquake which affected the Colonia Iulia Neapolis and which, in the middle of the 4th century AD, caused the disappearance of its port and the areas dedicated to fish salting. It is unlikely that Neapolis was affected by the violent earthquake of July 21st, 365 AD,which provoked a powerful tidal wave. Ammianus Marcellinus, a historian of late Antiquity, passed on the account of this catastrophe of universal dimension.

To the east of the fish salting district is the Nymfarumdomus: a sumptuous residence with aperistyle, dating from the 4th century AD, situated in the urban fabric and occupying an area of 1500 sq.m. An apse shaped basin, decorated on the inside with a mosaic representing a fine head of the god Oceanus, placed in the middle of a marine fauna, bears the inscription NYMFARVM DOMVS, Latin for the house of the Nymphs. This basin, located in the axis of a large ceremonial room (oecus-triclinium), offers hosts and their guests a beautiful perspective decorated with a mosaic  depicting two roosters facing each other on either side of an amphora filled with gold coins, revealing the wealth of the master of the house.Other mosaics, which decorate the rooms of this residence, relate to episodes from Greek mythology: the embassy of Chryses, priest of Apollo, to the Greek king Agamemnon ; the bath of the Nymphs in the Hippocrene source; the episode of Philoctetes incapacitated  and left behind on the island of Lemnos, with, next to him, the bows and the quiver he was bequeathed by Heracles; Poseidon saving the nymph Amymonae. These mosaics, today on display in the museum of Nabeul, testify to the refinement and the great classical culture of the owner of the house, who lived in the late Roman period.

To the north-west of the archaeological site, there is a thermal complex which was built, in the 4th century AD, in an area which was dedicated to the production of salted fish. Its components (apodytarium, tepidarium, caldarium and frigidarium) are distributed along an axial plan. Their floors were covered with mosaics. At the end of Antiquity, the thermal complex was transformed into a large mansion.

In the second half of the 7th century, and probably at the beginning of the 8th century too, a rural type housingscheme was established in part of the city.  And during the high Islamic period, the monuments of Neapolis had been used as a quarry for building materials for the city of Nabeul.