1911 Encyclopædia Britannica/Portus
PORTUS, an ancient harbour of Latium, Italy, on the right bank of the Tiber, at its mouth. For its origin see Ostia. Claudius constructed the first harbour here, 21 m. north of Ostia, enclosing an area of 170 acres, with two long curving moles projecting into the sea, and an artificial island, bearing a lighthouse, in the centre of the space between them; the harbour thus opened directly to the sea on the north-west and communicated with the Tiber by a channel on the south-east. The object was to obtain protection from the prevalent south-west wind, to which the river mouth was exposed. Though Claudius, in the inscription which he caused to be erected in A.D. 46, boasted that he had freed the city of Rome from the danger of inundation, his work was only partially successful. Nero gave the harbour the name of Portus Augusti. It was probably Claudius who constructed hither the direct road from Rome, the Via Portuensis (15 m.) which ran over the hills as far as the modern Ponte Galera, and then straight across the plain. An older road, the Via Campana, ran along the foot of the hills, following the right bank of the Tiber, and passing the grove of the Arval Brothers at the sixth mile, to the Campus salinarum romanarum, the saltmarsh on the right bank — from which indeed it derived its name (see Notizie degli Scavi, 1888, p. 228).
The site can still be fairly clearly traced in the low ground to the east of Fiumicino, and the lighthouse is represented in bas-reliefs. The harbour is generally supposed to have been protected by two moles with a breakwater in front, on which stood the lighthouse, with an entrance on each side of it. Trial soundings made in 1907 showed that the course of the right-hand mole is represented by a low sandhill, while the central breakwater was only some 190 yds. long, and probably divided from each of the two moles by a channel some 125 yds. wide. The existence of two entrances is, indeed, in accordance with the evidence of coins and literary tradition, though the position of that on the left is not certain, and it may have been closed in later times. The whole course of the left-hand mole has not yet been traced, but it seems to have protected not only the south-west but a considerable portion of the north-west side of the harbour. In A.D. 103 Trajan constructed another harbour farther inland — a hexagonal basin enclosing an area of 97 acres, and communicating by canals with the harbour of Claudius, with the Tiber direct, and with the sea, the last now forming the navigable arm of the Tiber (reopened for traffic by Gregory XIII. and again by Paul V.), and bearing the name Fossa trajana, though its origin is undoubtedly due to Claudius. The basin itself is still preserved, and is now a reedy lagoon. It was surrounded by extensive warehouses, remains of which may still be seen: the fineness of the brickwork of which they are built is remarkable. Farther to the east is a circular building in brick with niches; it is called the temple of Portumnus. To the east again is the so-called Arco di Nostra Donna, a gateway (possibly originally built by Trajan) in the fortifications which surround the port and are attributed to the time of Constantino. Many other remains of buildings exist; they were more easily traceable in the 16th century when Pirro Ligorio and Antonio Labacco made plans of the harbour. Considerable excavations were carried on in 1868, but unfortunately with the idea of recovering works of art and antiquities; and the plan and description given by R. Lanciani (Annali del instituto, 1868, 144 sqq.) were made under unfavourable circumstances. By means of these works Portus captured the main share of the harbour traffic of Rome, and though the importance of Ostia did not at once decrease we find Portus already an episcopal see in Constantine's time not very long (if at all) after Ostia, and as the only harbour in the time of the Gothic wars. Its abandonment dates from the partial silting up of the right arm of the Tiber in the middle ages, which restored to Ostia what little traffic was left. To the west of the harbour is the cathedral of S. Rufina (10th century, but modernized except for the campanile) and the episcopal palace, fortified in the middle ages, and containing a number of ancient inscriptions from the site. On the island (Isola Sacra) just opposite is the church of S. Ippolito, built on the site of a Roman building, with a picturesque medieval campanile (13th century ?); 2 m. to the west is the modern village of Fiumicino at the mouth of the right arm of the Tiber, which is 21 m. west-south-west by rail from Rome. It is a frazione, or portion of the commune of Rome. Three miles to the north is the pumping; station by which the lowland (formerly called Stagno di Maccarese, now reclaimed and traversed by many drainage canals) between here and Maccarese is kept drained (Bonifica di Maccarese) (see Tiber).
See H. Dessau in Corp. inscr. latin, xiv. i sqq. (Berlin, 1887); J. Carcopino in Notizie degli Scavi (1907), p. 734. (T. As.)