There was decay in some areas, but this late period was primarily one of transition; formerly filled with workers employed in collecting, storing and moving huge amounts of grain, oil, wine and other products to feed Rome, Ostia now assumed the character of a seaside resort.

By this time, the shifting course of the Tiber had landlocked the ancient port, and the town was mainly a shelter for the workers of the nearby salt mills.

In the late 15th century, the bishop Giuliano della Rovere (later Pope Julius II) commissioned the rebuilding of the main church and town walls under the direction of the architect Baccio Pontelli.

Ostia Antica is located in the south-western part of the municipality of Rome, separated from the urban complex, along the river Tiber.

Ostia Antica borders to the north with the municipality of Fiumicino, from which is separated by the stretch of the river Tiber between Ponte di Tor Boacciana and the Canale dei Pescatori.

The zone borders eastward with Zona Acilia Nord (Z. XXXII), whose boundary is marked by the Canale dei Pescatori, up to Via del Mare.