Back to menu

Introduction to Portus

The harbour of Claudius

Ostia had no natural harbour. Only the banks of the river could be used. Large ships had problems entering the river, because of a sand bar in front of the mouth. Therefore goods that arrived in large ships were often transferred to smaller ships on the sea. Large cargo ships could also be unloaded in the harbour of Puteoli, in the bay of Naples, after which the cargo was taken to Ostia in smaller ships. Finally, the Tiber quays simply did not offer enough mooring space for Rome's growing needs.

In 42 AD Claudius started the construction of an artificial harbour, a few kilometres to the north of Ostia. There seems to have been a small, natural bay or lagoon here that was incorporated in the harbour basin. The basin was protected by two curved moles, between which was a small island supporting a tall lighthouse: a long northern mole, and a shorter southern one. The width and length of the basin were c. 800 metres by a few kilometres! It was seven metres deep.

Map of Portus and Ostia. North is to the left.

Three channels connected the Tiber with the sea. One was to the north of Portus. It was probably meant for flood relief, and 20-35 metres wide. The second, to the east of the port, was curved and connected the Tiber with the third channel. This last channel ran to the south of the port and was 45 metres wide. It is known as the Fossa Traiani or Traiana, but it was made by Claudius. This channel was in the Middle Ages called Fiumicino ("Small river"), as is the modern village at the mouth of the channel (the river leading to Ostia was called Fiumara Grande). To the south of the basin was a small inner harbour. A short transverse channel, running from north to south, connected it with the Fossa. The Fossa also created an artificial island between Ostia and Portus, called Isola Sacra ("Sacred Island") in late antiquity, earlier Assis.

Capo Due Rami ("Head of the two branches"), where the Fossa Traiana (to the right)
branches off from the Tiber. Photo: Antonia Arnoldus-Huyzendveld.

The work of Claudius is mentioned in an inscription from 46 AD, possibly from the attic of an arch, which shows that Claudius also hoped to reduce the risk of inundations in the city of Rome, by digging channels from the Tiber to the sea:

TRIB(unicia) POTEST(ate) VI CO(n)S(ul) DESIGN(atus) IIII IMP(erator) XII P(ater) P(atriae)

Coins from 64 AD, so from the reign of Nero, celebrate either the completion of the work in 64 AD, or the 10th anniversary of the completion of the harbour. In any case, already in 62 AD the harbour was in use: in that year 200 ships in the basin perished during a storm. It has often been said that therefore Claudius' basin was unsafe, but it is more likely that the destruction was caused by a tsunami, the result of the same seismic activity that is documented in that year in Pompeii (the earthquake of February 5, 62 AD). On the coins the two moles are not identical. The one on the right (north) has arched openings. On some coins of the series (several dies were used) there seem to be a temple and an altar at the end of the left (southern) mole. The lighthouse is not depicted between the moles, but only a statue of an Emperor. Most archaeologists believe that in reality it stood on top of one of the floors of the lighthouse, as can be seen on a relief. The old reconstruction drawings show it as an isolated statue on a column. A reclining male figure with rudder and dolphin is the personification of the sea and the harbour.

Portus on a coin of Nero

Portus on a sesterce issued by Nero, in 64 AD.

In ancient literature the harbour is called Portus Ostiensis, coins minted in Rome have the text Portus Ostiensis Augusti ("the Ostian port of the Emperor"), while coins minted in Lyon, France only have Portus Augusti. Around the basin were commercial buildings and a small residential area, witness the presence of tombs. From the harbour the goods were taken to Rome in barges that were towed by men, in late antiquity by oxen. This final stage may have been limited to Fall and Winter, because of a low water table in Spring and Summer. Cargo arrived for the most part during Spring and Summer, the sailing season (mare apertum, "open sea"). Therefore warehouses (horrea) were needed in the port for temporary storage. The port had its own protective deities, the Lares Portus Augusti. The Imperial administration of the harbour was led by a procurator portus Ostiensis.

The harbour of Trajan

Trajan added a second, internal basin behind the basin that was dug by Claudius. It was hexagonal in shape, for harbours a unique shape. It has been suggested that it was designed by Apollodorus of Damascus, the architect of Trajan's forum in Rome. The work was carried out in the years 100-112 AD, and included improvements of the Claudian harbour. The sides of the hexagonal basin measured 357.77 metres. The maximum diameter was 715.54 metres. It was five metres deep. The bottom was covered with stones, at the north end gradually sloping upwards, to reach a depth of only one metre at the edge of the basin. In the quays were travertine blocks with holes, used for mooring, fifteen metres apart. Many new warehouses were built around the new basin, so that the total storage capacity was now much greater.

A mooring block. Testaguzza 1970, p. 104.

The basin could contain more than 100 ships that did not moor alongside the quays, but at a straight angle. It was surrounded by a few wide treads, leading to quays that were c. 6 metres deep. Columns with Latin numerals were found around the basin, suggesting that the sides of the hexagon were subdivided into numbered sectors. On the quays was a wall, with five narrow doorways on each side of the hexagon. The doorways are too narrow for wagons (1.80 m.). Apparently the goods were unloaded and carried by porters. This can also be seen on several reliefs and mosaics. The wall facilitated the control of the flow of goods, for the Customs Service and the levying of import duties (the portorium).

A Trajanic coin of the hexagonal basin.

A badly preserved inscription from the years 102-109 AD mentions Trajan, a channel and inundations of the Tiber:

[Imp(erator) Caes(ar) divi]
NE[rvae f(ilius) Nerva]
TRA[ianus Aug(ustus) Germ(anicus)]
DAC[icus trib(unicia) pot(estate) ---]
I[mp(erator) --- co(n)s(ul) --- p(ater) p(atriae)]
FOSSAM [restitui iussit]
[q]VA INVN[dationes Tiberis]
[ad]SIDVE V[rbem vexantes]
[rivo p]EREN[ni instituto arcerentur]

This second harbour was called Portus Traiani or Portus Traiani Felicis, "the port of the happy Trajan". The ports of Claudius and Trajan together were called Portus Uterque ("Both Ports"), but also Portus Augusti et Traiani Felicis.

A bridge named after Matidia, a niece of Trajan, spanned the Fossa Traiana, thus connecting Portus and the Isola Sacra. Fire-fighters (vigiles) were stationed in barracks. Several temples were built (significantly often with Greek dedications), including a temple of Liber Pater on a square used for auctions of wine. In front of this Forum Vinarium stood a colossal statue of an armoured Trajan, facing the entrance of the hexagonal basin. Houses and apartments have not yet been found in Portus. Initially many people working in Portus may have lived in Ostia, but in the later second century the famous physician Galenus wrote that both Ostia and Portus were populous centres. The habitations were then probably for the most part located to the south of the hexagon. The size of the population may have been in the order of ten thousand. Thousands of slaves must have worked in the harbour. Perhaps they lived on the upper floors of horrea, or outside the city.

Trajan's basin. Click on the photo for a larger image.
Photograph: Jan Theo Bakker.

Initially the administration of Ostia, so the city council (ordo decurionum) and magistrates led by mayors (duoviri), controlled Portus. The Imperial representative in the harbours was a procurator Portus. In Ostia the Imperial government was represented by a procurator Annonae, working for the praefectus Annonae in Rome. Trajan however seems to have withdrawn Portus from the jurisdiction of Ostia. The two harbour basins and the surrounding commercial buildings and infrastructure were from now on owned by the city of Rome. Ostia was the place where contracts and finances were discussed. Portus on the other hand was the place where the practicalities of the seaborne imports were handled, now overseen by a procurator Portus Utriusque, of "both harbours" (that of Claudius and that of Trajan, not Ostia and Portus).

Portus on a coin struck by Commodus, in 191 AD.

Late antiquity

An inscription informs us that part of Portus was named after Constantine and his family. The inscription was set up between 337 and 341 AD by the ordo et populus civitatis Flaviae Constantinianae Portuenses, that is by the people and city council of Portus, of the Flavian Constantine city (Portus was not alone in receiving this added name). It has been argued that a more precise date for the new name can be deduced from the emergence of a bishop from Portus in 314 AD, but using the argument is tricky. As Meiggs noted (p. 88): "Civil and ecclesiastical administration did not always coincide". The bishop, Gregorius, appeared at a council in Arles, France, and was said to be de loco qui est in Portu Romae, "from the place that is in the Harbour of Rome". Most likely this civitas (of which we hear nothing more) was merely the residential part of Portus. The commercial port is referred to as Portus Romae, still property of Rome. The Imperial official responsible for the port was now the praefectus Annonae himself, later a comes portus urbis Romae.

Legal sources (the Codex Theodosianus) document the activity in the harbour in the fourth and fifth century. We hear of weighers, porters, shippers of tow boats, ships arriving from Spain and so on. And there was renewed building activity. The temple of Liber Pater was restored. A Porticus Placidiana commemorated Placidia, mother of the Emperor Valentinian III. Christian churches appeared and a xenodochium, a guest house for pilgrims. But a city wall was also needed, and it was erected around 400 AD, incorporating parts of warehouses.

Portus was captured by Alaric and the Goths in 409 AD, and by the Vandals, led by their king Gaeseric, in 455 AD. The city was captured by the Goths led by Vitigis in 537 AD. This event was described in great detail by Procopius. The horrea were abandoned in the fifth and sixth century, collapsed, and were then used for burials. In the eighth century Trajan's basin became inaccessible due to silt brought in by the Tiber. In the ninth century there were invasions by the Saracens. These led to the foundation in 842 of the fortified settlement Gregoriopolis to the east of Ostia, by pope Gregorius IV. Pope Leo IV (847-855) restored the city wall of Portus and made gifts to a church. The last year in which we know that the harbour was still in use is 879 AD. Many churches stayed in use, witness a survey of the diocese of Portus in 1019. In 1190 Richard the Lionheart saw remains of the lighthouse and immense ruins. His visit is, as it were, a pivot between antiquity and the history of the excavations.

Reconstruction drawing of Trajan's harbour, seen from the north.
Click to enlarge. Testaguzza 1970, p. 154-155.

Some depictions of the harbour

Unloading a ship

This relief was found in Portus. Amphorae are being carried from a ship to the quay. The three seated persons seem to take notes about the cargo on wax tablets, joined together like a book. The first porter seems to receive some kind of token.

Relief depicting the unloading of a ship. From Pavolini 1986, fig. 26.

Unloading a ship

A scene similar to the one above is depicted on a Roman sarcophagus.

Sold by Christies in 2020.

Transportation of wild animals

A ship approaches the lighthouse. On board are lions in cages, destined for the amphitheatre, but first taken to a vivarium to the east of Ostia, or to another one near Rome.

Relief of a ship carrying lions. From Pavolini 1986, fig. 27.

A bar

This relief is on a sarcophagus from the Isola Sacra necropolis. To the left a ship is approaching the lighthouse. It is accompanied by a small boat. To the right is a bar, visited by the crew after mooring the ship. The left part of the bar is reminiscent of the Caseggiato del Termopolio in Ostia. A dolphin seems to be depicted here, perhaps indicating the name of the bar.

Relief with a harbour scene and a bar. From Meiggs 1973, Plate XXVI, b.

A city plan

Below is a fragment of a marble plan of Portus (18 x 16.5 cm.). The fragment was reused in the tomb of Iulia Procula, in the Isola Sacra necropolis. The many holes were made when the fragment was reused. The length of facades is indicated by numbers: CLVII[..], CCXXIX, and C[....]. Two triangles represent staircases. The area that is depicted measures c. 41 x 37 metres.

Fragment of a marble plan of Portus. From Rodriguez 2002, Tav. VI.

[jthb - 11-Jul-2020]