The Claudian Harbour (Tiber delta): a “Fluvial Pompeii”

This blog post ties into the exhibition “Claudius: An emperor with an extraordinary fate” that has toured around France and Italy. This exhibit featues the life and achievements of the Roman Emperor, Claudius, who was born in Lugdunum (modern day Lyon) and reigned during the 1st c. AD. The Musée des Beaux Arts de Lyon hosted this exhibition during winter 2018 and spring 2019. The exhibition is currently in Rome at the Museo dell’Ara Pacis and will be opened from 6th April – 27th October 2019. A catalogue of the exhibition, produced with the support of the Fondation de l’Olivier is available: Claude (Lyon, 10 av. J.-C. – Rome, 54 ap. J.-C.). Un empereur au destin singulier (320 pages, 234 illustrations. Paris, Lienart éditions) for 38 €.

During the 1st c. BC, Rome became the most populous city in the Mediterranean world with one million inhabitants. In order to supply Rome’s growing population, supply ships were docked in the harbour of Pozzuoli, located ~200 km south of the capital. Since the 2nd c. BC, Pozzuoli was a major Roman port with the ability to accommodate large ships. Pozzuoli’s natural rocky bay landscape was ideal for constructing a port because it was not affected by high fluvial sedimentation, a problem that was notorious in its smaller sister port in Ostia. Once the ships were unloaded in Pouzzuoli, the goods were transported to Rome by land through the Appian Way or by sea (cabotage) using smaller vessels along the coast to Ostia and later down the Tiber River. By the end of the 1st c. BC, Rome suffered a famine and demands from the capital were increased rapidly as a result. However, transportation of goods through the Pozzuoli-Ostia-Rome route was no longer sufficient because it was difficult to meet the demands and cope with the high sedimentation in the port of Ostia (Goiran et al., 2014; Zevi, 2002; Keay & Paroli, 2011). Thus, in 42 AD, Emperor Claudius ordered the construction of a large port basin located on the Tiber delta. Known as the Claudian Harbour, it was built 25 km downstream of Rome and 3 km north of the city of Ostia (Fig. 1). In the 2nd c. AD, Emperor Trajan completed the system by digging an additional 33 hectare hexagonal basin, making this the largest port in the ancient Roman world, known as Portus.

Fig. 1: Map of Danti, the ruins of Claudian Harbour observed in 1582

The decline of Rome at the end of the 5th c. AD resulted in the gradual abandonment of Portus. As engineers abandoned their responsibilities of maintaining the port’s Tiber River deposits over time, the basin became infilled and its port infrastructures (e.g. moles, quays, etc.) were covered as a result. In one millennium, the shoreline had prograded 2 km from the ancient coastline covering most of Portus because of high sedimentation from the Tiber Delta (Bellotti et al., 2007; Salomon, 2013).

As the Tiber alluvial deposits became evident in the harbour basin, Portus was nicknamed as the “Fluvial Pompeii.” Claudius’ original harbour configuration remains highly debated between scholars to this day.

Fig. 2: Map of Danti, the reconstruction of Claudian Harbour after Danti, 1582

During the Renaissance in the 16th c., Pope Gregory XIII asked Ignazio Danti to paint 40 frescos in the Vatican Map Gallery. Two of Danti’s frescos depict Portus. One of the frescos illustrates the archaeological remains he observed in 1582 (Fig. 1), and the second (Fig. 2), is a reconstruction of the Portus at the height of its power in ancient Rome. The Claudian Harbour is clearly illustrated with two offshore moles built towards the sea, with an entrance located to the west (Fig. 3a).

Fig. 3: Hypotheses on the configuration of Claudian harbour basin (be mindful that figure 3 is looking South, the West is at the right). Figure from Testaguzza 1970, modified by J.-P. Goiran © CNRS – UMR 5133
3a) The hypothesis showing a major entrance in the west before the frescos by Danti. 3b) Illustrated the hypothesis featuring a major entrance to the north, according to O. Testaguzza’s obersrvations. 3c) Depicts the reconstruction of the Claudian harbour based from sediment coring results. The results show a basin with two entrances, the main one to the west and a secondary one to the north.

Four centuries later, at the time when Rome’s international airport was underway in the 1960s, an Italian engineer Otello Testaguzza uncovered new remains of port structures dating to Emperor Claudius and proposed a new hypothesis. Testaguzza argued that there was no entrance in the west because based on his observations there was an accumulation of sand forming a sand dune with a south-northern orientation (Testaguzza 1970). As such, Roman engineers would have used this sand dune as a natural structure protecting the basin from the western offshore swells. With the sand dune in the west, the Romans would have built the east-western oriented mole with an entrance opening to the north at the end of the mole (Fig. 3b). Unfortunately, with the construction of Rome’s international airport in this area and decisions made by the city of Fiumicino’s authorities, further excavations in the area were not permitted.

In order to explore Testaguzza’s hypothesis regarding a possible sand dune at Portus, scientists from French, Italian, and British institutions used geoarchaeologial methods involving mechanical coring to obtain sediment archives for laboratory analyses of the study area. Over the past few decades, these research teams have been attempting to determine the complete structure of the Claudian Harbour moles and the location of its entrance(s). Figures 3a and 3b summarize the two hypotheses regarding the entrances of Portus and the paleoenvironmental reconstruction of the sediment archives obtained from the study area.

Based on the results in Figure 3, if there were to be a west entrance (Fig. 3a), the cores should depict a deep basin in the western sector and the “terra ferma” in the area of the northern entrance proposed by Testaguzza. For the hypothesis describing a northern entrance, marine sediments should be found in the north and there should be evidence of a dune to the west. However, according to the results, the cores have marine sediments present in the northern sector of the cross-section that were deposited in an ancient entrance (Goiran et al., 2010). On the west side, there is no evidence of a sand dune but the cores illustrate a 6 m depth of the Claudian harbour basin. In other words, the two initial hypotheses were not contradictory but complementary. Based on the findings in this report, the Claudian Basin had two entrances, a major one to the west and a secondary to the north.” (Fig. 3c).


Ecole Française de Rome, The British School at Rome, Soprintendenza speciale per i Beni Archeologici di Roma – Sede di Ostia, ANR, ERC Portus-Limen, University of Southampton, Université de Rome – La Sapienza, Université Lyon 2, CNRS and W.M. Chan for the English translation.


Goiran, J. P., Tronchère, H., Salomon, F., Carbonel, P., Djerbi, H., and Ognard, C. 2010. Palaeoenvironmental reconstruction of the ancient harbors of Rome: Claudius and Trajan’s marine harbors on the Tiber delta. Quaternary International 216 (1-2), 3-13.

Salomon F. 2013. Géoarchéologie du delta du Tibre: Evolution géomorphologique holocène et contraintes hydrosédimentaires dans le système Ostie – Portus, thèse de Doctorat en géographie de l’Université de Lyon 2.

Testaguzza, O.1970. Portus. Julia ed.

Bellotti P., Calderoni G., Carboni M. G., Di Bella L., Tortora Valeri P., and Zernitskaya V. 2007. Late Quaternary Landscape Evolution of the Tiber River Delta Plain (Central Italy): New Evidence from Pollen Data, Biostratigraphy and 14C Dating, Zeitschrift Für. Geomorphologie 51 (4), 505–534.

Goiran J.-P., Salomon F., Mazzini I., Bravard J.-P., Pleuger E., Vittori C., Boetto G., Christiansen J., Arnaud P., Pellegrino A., Pepe C., and Sadori L. 2014. Geoarchaeology Confirms Location of the Ancient Harbour Basin of Ostia (Italy), Journal of Archaeological Science 41, 389–398.

Keay S. and Paroli L. 2011. Portus and Its Hinterland: Recent Archaeological Research, Archaeological Monographs of the British School at Rome 18, London, British School at Rome.

Zevi F. 2002. Origini Di Ostia, in : C. Bruun & A.G. Zevi  (éds), Ostia e Portus Nelle Loro Relazioni Con Roma, Rome, Institutum Romanum Finlandiae, p. 11–32.


Jean-Philippe Goiran est Chargé de Recherche au CNRS. Géo-archéologue, il travaille sur l’histoire des ports antiques et les paléoenvironnements littoraux et deltaïques. UMR 5133 – Archéorient, Maison de l’Orient et de la Méditerranée, Lyon.

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Jean-Philippe Goiran (2019, 17 mai). The Claudian Harbour (Tiber delta): a “Fluvial Pompeii” ArchéOrient - Le Blog. Consulté le 19 mai 2024, à l’adresse

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