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A large artificial harbor built by Claudius 3.2 km N of the mouth of the Tiber. It was partly excavated from land in a bay and was protected by two moles enclosing an area roughly circular in shape with a maximum diameter of ca. 1000 m. The most spectacular feature of this harbor was a grand lighthouse for the foundations of which Claudius used the gigantic merchantman built to transport from Egypt the obelisk that was erected in the circus beside the Vatican hill. The vessel was filled with concrete and sunk to form ca. 90 m of the left mole some 200 m from its end. The new harbor was not a complete success, for 200 ships in harbor are reported by Tacitus to have been lost in A.D. 62. It was partly for this reason that Trajan added to the Claudian harbor a large hexagonal basin with sides measuring 358 m. Claudius had linked his harbor with the Tiber, and thus with Rome, by two canals, which Trajan replaced with a single new canal.

In 1925, when Trajan's basin was restored to approximately its original state, the main features were studied before it was filled. In the retaining walls large travertine mooring blocks were still in place, and there had been small columns with numbers round the basin, probably to identify berthing stations. Six meters from the quayside runs a wall which facilitated control, and the narrowness of the doorways shows that carts were not used to carry cargoes to the warehouses. The coins commemorating Trajan's harbor show warehouses round all sides except the NW. Most of the storage available was used for grain, but some sections were reserved for other commodities. A relief in the Torlonia Museum shows a merchantman unloading wine and in the background a statue of the wine god. A small circular peristyle temple of Liber Pater was found on the NE side of the harbor. The neighboring quay may have been reserved for the wine trade. Trajan's coins suggest that the buildings on the NW side of the harbor were different and this was confirmed by 19th c. excavations, which found traces of a small theater, baths, and a series of rooms round a large atrium. This is probably where the imperial procurator responsible for the control of the harbors had his headquarters and where the emperor would stay on official visits.

The harbor plans probably did not provide a residential area for the required labor force, but there had to be a nucleus of residents for emergencies, including a detachment of vigiles to fight fires, and the settlement was bound to grow. By the time of Constantine the harbor population was sufficiently large to manage its own affairs with the proud title of Civitas Flavia Constantiniana. The line of the brick-faced walls which were built at or near this time indicates the general plan. The two main housing areas were to the S between the harbor and Trajan's canal and in a large triangle to the E. It is at the apex of this triangle that the road from Rome enters the town by the Porta Romana and the aqueduct followed the line of the road. Of the buildings in this area only a large unidentified circular peristyle temple survives above ground near the gate. In the S area a Christian basilica has been traced, attached to which was a rest house for pilgrims built by the patrician Pammachius. South of the canal the elegant mediaeval campanile of S. Hippolito commemorates a martyr of Portus. The two main necropoleis developed along the roads that led to Rome and to Ostia. A large number of tombs excavated in the latter are among the best preserved in the Roman Empire, illustrating the transition from cremation to burial, which was completed by the end of the 2d c.

In the Late Empire Portus remained vital to Rome. Though it was sacked by Alaric in 408, one of its most famous monuments was built ca. 425, a marble colonnade stretching along the north bank of the canal for some 200 m, Porticus Placidiana. But by the 6th c. the harbors were silting up and grain from overseas was no longer essential for the maintenance of Rome's heavily reduced population.


G. Lugli & G. Filibeck, Il Porto di Roma lmperiale e l'Agro Portiense (1935); G. Calza, La Necropoli del Porto di Roma Imperiale nell'Isola Sacra (1940); O. Testaguzza, Portus (1970); R. Meiggs, Roman Ostia2 (1974).


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