Perhaps the earliest of Rome’s colonies that was inhabited exclusively by its own citizens was Ostia, established at some point after the mid-4th century BC. Originally the colony was tiny, estimated to have covered 2.4ha. It was enclosed by rectilinear fortifications and it is also believed to have had an orthogonal street system with the same orientation as the walls. It was located not far from Rome on the Tyrrhenian coast near the mouth of the Tiber, and its function is believed to have been to defend this stretch of coast and the entrance to the river.
After the foundation of Ostia, ancient literary sources indicate that Rome founded a further 21 coastal colonies of Roman citizens down to the year 181 BC and the archaeological sites of all but two of them have been found with relative certainty. Archaeologists and historians cannot claim to know all the reasons why these colonies were founded. Ancient literary sources contain reports of seaborne raiders active in the waters of the Italian coast, however, and Rome considered the maritime power of Carthage to be a threat. Tensions between Rome the Punic city grew during the 3rd century BC, leading to open conflict for the first time in 264 BC.
Similar to Ostia, many of the Roman citizen colonies of this period were small, although not of uniform size, with rectilinear fortifications. The construction of straight fortifications with right angled corners is, above all, a response to building on level terrain, and many of these centres were located on coastal plains. To a certain degree, the colonies can be considered as permanently manned forts. Perhaps as many as 13 (of 21) of them were founded as completely new settlements, with the remainder being set up within or very close to pre-existing centres.
One of those of the latter category was Pyrgi, believed to have been the port-town of the great Etruscan centre of Caere (Cerveteri). It is located about 45km to the NW of Rome and has archaeology dating back to the 8th century BC. In fact, it is probably best known for its pre-Roman history. There are strong indications that it was frequented not only by Etruscans, but also by Greeks and Phoenicians. It possessed two great sanctuaries, in one of which temples of the 6th and 5th centuries BC have been excavated.
At some point, probably in the first half of the 3rd century BC, the Romans’ dominion over the local area is reflected in their founding of a colony at the site of the Etruscan port. Rectilinear walls were constructed, enclosing an area of 5.7 hectares, that seem to have been orientated on the line of the coast. It has been presumed for many years that the other rectlinear citizen colonies were planned in a similar way to Ostia, with orthogonal street-systems that were orientated according to the line of the walls.
Yet recent excavations at Pyrgi by Flavio Enei and his team have produced results that have shattered the simple logic of this presumption. It seems as though the Roman colony was built directly on top of the Etruscan settlement, although the Roman centre only occupied about half of the area of its Etruscan predecessor. Roman Pyrgi had a rectilinear street-system, but it turns out that it was not orientated on the Roman walls. It seems that Etruscan Pyrgi already had an orthogonal grid of streets in the Archaic period, and the Romans adapted it for their colony’s street system. But the orientation of the Etruscan streets was close to being diagonal to the line of the walls, although it is not yet clear whether the whole of the Roman urban area was laid according to this alignment. The reasons why the Romans chose to maintain the Archaic planning is not clear, especially because a destruction layer was found associated with the period of the Roman takeover, suggesting that some or all of the former Etruscan structures were destroyed before the colony was founded. This destruction layer makes it less likely that the reason for the maintenance of the Etruscan orientation was related to the desire to preserve pre-colonial buildings. A fascinating riddle.
At some point during the first two decades of the 2nd century BC, the character of citizen colonies changed. New ones, such as Luni, were founded as much larger urban settlements than their 3rd century-BC predecessors. Several of the older small colonies were enlarged during the 2nd century and took on much more recognizably urban characters. This reflects the fact that the Roman concept of the colony changed over the centuries of Roman rule.
At Pyrgi, a castle was built during the 14th century within the walls of the former colony: the castello di Santa Severa. It still stands (see image) and is often open for visitors during the summer.
Enei, F. 2012 ‘Pyrgi e le sue mura poligonali: recenti scoperte nel castrum e nell’area portuale’, in L. Attenni and D. Baldassarre (eds.) Quarto seminario internazionale di studi sulle mura poligonali. [Alatri] Palazzo Conti Gentili, 7-10 ottobre 2009. Roma: Aracne, 313–325.