The oldest actual remains have been dated to the fourth century BC.
In the early third century a military fort (the so-called Castrum) was built for defensive purposes at the mouth of the river Tiber.
In the third century BC Ostia was primarily a naval base.
In 267 BC it became the seat of one of the quaestores classici (quaestors of the fleet), the quaestor ostiensis.
During the Punic Wars Ostia played an important role as military harbour, and for that reason the inhabitants were freed from military duties.
In the second century BC Ostia gradually changed to a commercial harbour. The quaestor now supervised the import of grain.
In 87 BC the city was occupied and destroyed by Marius. New town walls were built by Cicero, after destruction of the city by pirates in 67 BC.
The first year mentioned in the local calendar, the Fasti Ostienses, is 49 BC. In the early first century after Christ the first forum there was built by Tiberius (14-37).
The city was still relatively insignificant however. The shoreline near Ostia offered no natural protection to ships.
Small boats could sail up the Tiber to Rome. For large ships Ostia was a dangerous place.
To handle the increasing traffic, larger harbours were built during the reigns of Claudius and Trajan, at which time the city may have boasted a population as high as 60,000.
It then served as the port city for the capital, with the wealth of the empire passing through its harbour.
The eventual silting of the harbour led to the decline of Ostia, beginning in the third century of the modern era, a hundred years before the birth of Augustine.
A diminished population continued to live there until the ninth century when the site was abandoned.
Because the site was quickly covered over and remained undisturbed for centuries, excavations at Ostia have produced many stunning finds, including the remains of hundreds of buildings and over 4,000 inscriptions.
It stands second only to Pompeii in presenting us with a portrait of a Roman city in the early empire.
Ostia today is a beach area, but in the time of Augustine it was a commercial centre and the port of the City of Rome.
Ostia Ruins in photographs - Hundreds of Ostia photographs by classicist and teacher, Leo Curran of the University of Buffalo, New York State. This web site is a labour of love, diligently executed. It is actually three sites: