Historical background

By S. Keay

The Portus Augusti was an artificial port that was established by Claudius in AD 46 and inaugurated by Nero in AD 64, and which now lies c. 3km inland. It needs to be understood in relation to both Ostia, for which it provided much needed anchorage capacity, and Rome, which it came to serve as its principal maritime port (Meiggs 1973; papers in Bruun and Gallina Zevi 2002). The early port comprised a huge artificial basin for safe anchorage as well as a smaller basin (the Darsena) and warehouses (Keay et al. 2005). Two canals linked the complex to both the Tiber and the Tyrrhenian sea, enabling a much more rapid movement of cargoes in the service of the annona up to Rome than had been possible before, while at the same time attempting to provide flood relief to the lower Tiber valley and Rome itself. Portus was substantially enlarged under Trajan between c. AD 112-117 with the addition of a second and smaller inner basin of hexagonal form, as well as a range of warehouses, temple and other buildings and a transhipment canal. Epigraphic, archaeological and some historical evidence points to an intensive use of the port during the 2nd and 3rd c AD, with major building episodes under the Antonine and Severan emperors. It was also very active in the 4th c AD. A Bishop of Portus is recorded as having attended the Council of Arelate in AD 314, while an inscription dating to AD 337-45 records that under Constantine the port was recognized as a municipality independent of Ostia, which at this stage is generally understood to have been in decline. Furthermore, edicts recorded in the Theodosian Code attest to the care exercised by successive emperors in regulating the use of the port throughout the 4th century. Despite being sacked by Alaric the Visigoth in AD 409, and perhaps again by Gaiseric the Vandal in AD 455, historical sources and archaeological and epigraphic evidence point to the sustained use of the port until the later 5th c AD. At this point, however, there is a marked change in its tempo, with the construction of a stout defensive wall around the Trajanic basin and surrounding buildings, and a sharp drop in the range of imported ceramics to the site. The port was subsequently the focus of a ten-year struggle for control between Ostrogothic and Byzantine forces during the Gothic Wars (AD 536-552), which ultimately resulted in Byzantine victory. Following these events, commercial activity at the Byzantine port was even further reduced and focused upon the Trajanic basin and the area around the basilica portuense (Maiorano and Paroli 2013: 365-75) with many parts of the earlier port being used for burials. Historical and archaeological evidence indicates that following the collapse of Byzantine control in central Italy, Porto retained some kind of maritime role under papal control until at least the 11th c (Wickham 2015: 100-8).

Archaeological background

By S. Keay

The site of the port has been a focus of interest since at least the 16th c, but was not the subject of sustained study until the late 19th c (Lanciani 1865) and early 20th c (Lugli & Filibeck 1935). More recently, however, it has benefitted from a range of broad historical (Meiggs 1973) and archaeological (Testaguzza 1970; Mannucci 1992; Keay et al. 2005) studies.

By the mid to later second century AD the port complex comprised three key elements. The first was the Claudian basin (200 ha) that was enclosed by two large artificial moles to the north and the south, and with a centrally placed lighthouse (pharos) that projected into the sea to the west (Morelli et al. 2011). The basin had a depth of up to eight metres and must have, therefore, acted as a space for the mooring of sea-going ships waiting to pass through the Canale di Imbocco al Porto di Traiano and unload in the hexagonal basin; it could also have enabled sea-going ships to tranship onto smaller boats (Boetto 2010). The second basin, the Darsena, was a rectangular (1.07 ha) and lay to the south. It had a depth of c. 6 m and seems to have provided anchorage for the smaller boats (naves caudicariae) that would have moved down the Canale Trasverso to access the Fossa Traiana to the south. It was delimited on its northern side by the Grandi Magazzini di Traiano complex and by the so-called Foro Olitorio to the south. The hexagonal basin of Trajan, the third basin (32 ha) lay a short distance inland of the Claudian basin to the east. It had a depth of seven metres and was the core of the harbour system at Portus. Sea -going ships entering the basin from the Canale di Imbocco al Porto di Traiano could have anchored temporarily at the centre until such time as a mooring space along its edges became free, while the regular sequence of numbered columns and mooring rings suggests that there was a strict order and procedure in docking the ships. Altogether these three basins provided c. 233.07 ha of basin space and would have absorbed most of the goods imported to Portus and onwards to Rome, and presumably included most of those that were subsequently transported southwards to Ostia (Keay 2012a).


Two large buildings at the centre of the port were the focus of the port authority (see papers in Keay and Paroli 2011). The first was the Palazzo Imperiale, a unique complex (3 ha) that was completed c. AD 117, whose principal western façade opened on to the Claudian basin while its southern frontage dominated side VI of the Trajanic basin. Specific activities centred here might have included the coordination of the movement of sea-going ships between the Claudian and Trajanic basins, sequences of mooring and unloading cargoes, associated charges, the assignment to warehouses and the rental of space therein. Adjacent to this to the east was the second building, a massive oblong rectangular complex that opened on to both the Trajanic basin and the Claudian basins. The third structure was the Grandi Magazzini di Settimio Severo, a late second century AD complex that was immediately adjacent to the south-western corner of the Palazzo Imperiale, and physically joined to it at a later date.


It is well known that the hexagonal basin was surrounded on four of its six sides by large oblong buildings traditionally identified as warehouses, and together represent an increase in warehouse space to from 32, 790 to 59, 488 m2. Recent work, however, suggests a rather more complex picture with significant functional differences in the buildings along its six sides. The northern side (I) was bordered by an oblong warehouse, behind which there was a sprawling burial area of lower status, possibly servile, burials. The western side (II) opposite the entrance (V) was dominated by a temple complex between double pairs of oblong warehouses, behind which there seems to have been building that was largely ephemeral in nature. The southern side (IV) was distinguished by two warehouses defining a triangular space. There is as yet, however, little evidence as to the nature of the commodities stored in any of the warehouses at Portus, although grain is often assumed to have been the principal commodity.


It is also worth noting that there is evidence for the provision of a substantial internal wall running around at least two sides (III and V) of the hexagonal basin at some stage in the post-Trajanic period, which was pierced by small openings which would have effectively funnelled the movement of cargoes into warehouses through re-arranged points, suggesting that there was a degree of centralized control in regulating the movement of cargoes in and out of warehouses.


Aside from buildings directly connected with the commercial and administrative life of the port, there is very little evidence for any residential occupation, unlike at Ostia. The most likely focus for what there was lay in the area between the triangular warehouses running along the south side (IV) of the hexagonal basin and the Canale Trasverso to the west, together with small temples and other official structures. There was additional settlement on the southern side of the Fossa Traiana on the Isola Sacra. This was relatively limited although it was complemented by some public buildings, including a bath block and possible Isaeum. A major cemetery lay to the south of it on either side of the Via Flavia (Calza 1940; Baldassare et al. 1996).


Recent geophysical survey (Keay et al. 2005) has revealed the existence of a range of warehouses and other structures between the aqueduct and road and the transhipment canal (Canale Romano) that ran between the Tiber and the hexagonal basin; beyond this there was a small river port. Much of this land was given over to burial in the mid and later imperial period. The flat land that lay to the north-east of this and south of the Stagno Maccarese was known as the Campus Salinarum Romanarum and was given over to salt extraction (Morelli et al. 2008). This had begun prior to the establishment of the port during the Republic, but continued under the Empire, taking advantage of the Via Campana/Portuensis to transport it to Rome. It remained a source of wealth into the Medieval period.


Grain was clearly one of the principal commodities imported to Portus, principally from north Africa and Egypt as part of the annona destined for Rome, and stored in some of the larger warehouses across the site (viz. the Grandi Magazzini di Traiano). Olive oil from southern Spain (Baetica) played a similar role. In terms of its broader commercial role, research into ceramics from different excavations at the site suggests that the port received imports primarily from Africa and Tripolitania, to a lesser extent southern and eastern Spain and southern Gaul, and rather less from different parts of the eastern Mediterranean. Marble was deposited in the marble yards (statio marmorum) on the southern bank of the Fossa Traiana, prior to being moved up-river to the statio marmorum at Rome from the late first century AD onwards. Material from the site points to the presence of a wide variety of material from the east Mediterranean, and to a lesser extent North Africa (see papers in Keay 2012).

Geomorphological background

By F. Salomon and J.-P. Goiran

Portus was situated in a marginal estuarine landscape close to the mouth of the Tiber, some 35km from Rome. Portus lay 2km to the north of Ostia, arguably within its territory, and was situated close to a key bend in the Tiber to which it was connected by a canal. . Today, the remains of the harbour lie inland, trapped by sediments deposited over the last 2000 yrs. Indeed, the Tiber delta has developed and the coastline moved around 4km towards the west between the middle of the 1st c. AD and today (Le Gall 1953; Bersani and Moretti 2008). Portus was composed of two harbour basins: (1) an outer basin excavated by the emperor Claudius that was subject to swells and now filled by sands; (2) a well-protected inner hexagonal basin partly filled by silts and clays (Goiran et al. 2010) and which still has water in it today.


Over the last 10 years, many geoarchaeological teams have focused on these basins. Some has studied the configuration of the basins and their bathymetry (Giraudi, Tata, and Paroli 2009; Bellotti et al. 2009; Goiran et al. 2011; Morelli, Marinucci, and Arnoldus-Huyzendveld 2011), hydrodynamism (Giraudi, Tata, and Paroli 2009; Goiran et al. 2010), marine/fluvial water and sediment inputs (Goiran et al. 2010; Sadori et al. 2010; Mazzini et al. 2011; Pepe et al. 2013; Salomon et al. 2012; Delile et al. 2014) and current modelling (Noli and Franco 2009; Millet, Tronchère, and Goiran 2014). Other research has been targeted at locating the coastline prior to the establishment of the Claudian harbour (Arnoldus-Huyzendveld 2005) the geomorphological units that pre-dated the harbours (Morelli 2005; Goiran et al. 2007; Giraudi, Tata and Paroli 2009; Bellotti et al. 2011) have also been identified. All of these studies are based on a general understanding of the formation of the Tiber delta during the Holocene (Bellotti et al. 1989; Bellotti et al. 1994; Giraudi 2004; Bellotti et al. 2007; Milli et al. 2013). The identification of the biological sea level dating to between the 3rd – 5th c. AD (Goiran et al. 2009) suggests that it was c. 80 cm below the current sea level, a fact that is of key importance for determining the depth of the ancient harbour. The other focus of geomorphological research has been the canal that played a key role in the functioning of the port (Salomon et al. 2012; Salomon 2013; Salomon et al. 2014).

Importance in the Roman harbour network

By S. Keay

The key to Portus’ success in feeding the City of Rome was the high degree of connectivity that existed between what one might term the different micro-regions within the port, and between it, Ostia and Rome (see Keay 2012a; see also Brandt 2005); it also underwrote the close administrative links between them (Bruun and Gallina Zevi 2002). This inter-communication was achieved by means of a network of roads and canals articulated around the Tiber itself. Aside from the Fossa Traiana and northern canal of likely Claudian date, the port was served by a transhipment canal (Canale Romano); this ran from the Fossa Traiana past the hexagonal basin and onwards to the Tiber. There was also a major canal that ran southwards from the Fossa Traiana towards Ostia, parallel to the Via Flavia. Portus was also connected to Rome by the key land route along the Via Campana/Portuensis (Loreti 2006).


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