A settlement known as an oppidum was established by individuals belonging to the Latial culture around the eleventh century BCE or the start of the first millennium BCE. Subsequently, it became the primary fortress of the Volsci people until it was eventually seized by the Romans in 338 BCE. According to certain traditions of Rome's founding legend, Antium was established by Anteias, the offspring of Odysseus.

During the Iron Age (circa ninth till seventh centuries BCE) the city of Antium was founded on the Vignaces plateau (the present district of Santa Teresa) having control of an important seaport along the shipping routes of Magna Graecia, Rome and Etruria joined by a road network to the cities of the hinterland (Colli Albani, Palestrina, Gabii). The skill of the pirates of Anzio was often cited in Latin documents, both at the time of Volscians ruled the city (fifth century BCE) and after, during the conflict between Romans and Latins (fourth century BCE). After the Roman conquest, the political regression of the city, together with the advance of the coastline led to the original port being abandoned and subsequently, the decline of the navy of Anzio. In the first century BCE, the Greek geographer Strabo describes the city as having "no port" at all. The ruins visible today are those of the large part built by Nero to encourage commerce along the Tyrrhenian routes. The complexity and vast expanse of this construction were noted by the historian Gaius Suetonius Tranquillus in his life of Nero.

The jetties, which are still partly visible between the lighthouse and the port of Innocenzo, were constructed using millions of cubic meters of cement cast in a series of articulated wood form work with reinforcement piling. Traces of this form of work can be clearly seen amongst the remains. Parts of the stores which were located round the quay of the port (the so called grotta Neroniane) can also be identified at the Capo d'Anzio.

circa 150 BCE - 100 CE

Imperial Villa
The different phases of construction of the villa can be clearly seen in the area near the modern day lighthouse. Between the middle of the second century BCE and the end of the first century BCE this was the site of a dwelling made of square blocks of local sandstone (macco) and opus incertum, of which paving in cocciopesto or Opus signinum (pulverised shard) and multicoloured mosaic with geometric motif remains. The main areas are arranged around a central triclinium following the classical layout of a Roman house.

During the second phase, perhaps that of an Augustan period, the Republican complex was completely demolished to make way for a large exedra - a rectangular garden more than 170 meters in length, probably having a colonnaded sea front.

The construction of the nearby Neronian port, together with the progressive enlargement of the city resulted in the great exedra and adjoining gardens losing their function as a private retreat and this part of the villa was subsequently modified; the exedra was replaced by a series of areas for entertaining having foundations in opus reticulatum (Opus reticulatum) with tiled walls, and massive pillars at regular intervals opening on to a central area. These modifications can be dated from between the Neronian and Flavian eras (second half of the first century BCE).