Ostia thus lost a considerable amount of its trade, but its im portance still continued to be great. The 2nd and 3rd centuries, indeed, are the high-water mark of its prosperity: and it still possessed a mint in the 4th century A.D. The first bishop of Ostia of whom we have knowledge dates from A.D. 313, and the first bishop of Portus from about the same time. Both sees exist ; the former is held by the dean of the College of Cardinals.
During the Gothic wars, trade was confined to Portus and the ravages of pirates led to the gradual abandonment of Ostia. Gregory IV. constructed in 83o a fortified enceinte, called Gre goriopolis, in the eastern portion of the ancient city, and the Saracens were signally defeated here under Leo IV. (847-856). The battle is represented in Giulio Romano's fresco from Ra phael's design in the Stanza dell' Incendio in the Vatican.
In the middle ages Ostia became a quarry for the cathedral of Orvieto, etc., some of its marbles being conveyed by the Pisans as far as Sardinia. Later it regained something of its importance owing to the silting up of the right arm of the Tiber. In 1483-1486 Giuliano della Rovere (nephew of Pope Sixtus IV., and afterwards himself Pope Julius II.) caused the castle to be erected by Baccio Pintelli, a little to the east of the ancient city. It is built of brick and is one of the finest specimens of Renaissance fortification, and exemplifies especially the tran sition from the old girdle wall to the system of bastions : it still has round corner towers, not polygonal bastions. An agricultural colony, founded after 1875, and consisting mainly of cultivators from the neighbourhood of Ravenna, has produced a great change for the better in the condition of the place. The modern village is part of the commune of Rome. The marshes have been drained, and a pumping station erected near Castel Fusano. An electric railway has been constructed from Rome to Ostia and thence to the sea-bathing resort of Ostia Mare.
Excavations on the site of Ostia were only begun towards the close of the 18th century, and no systematic work was done until 1854, when under Pius IX. a considerable amount was done (the objects are now in the Lateran museum). The Italian Government laid bare many of the more important buildings in 188o-89: and resumed work in 1907. Owing to the fact that the site is largely covered with sand and to the absence of any later alterations, the preservation of the buildings excavated is very good, and Ostia is, with the exception of Pompeii, the best example in Italy of a town of the Roman period, while its houses, the massive concrete walls of which were faced with brick and reticulate work (both as a rule left unplastered on the outside) rose to a height of three or four storeys and had balconies and numerous windows. They were frequently planned like modern apartment houses, and show us what the ancient Roman insula or block was. On the east the site is approached by the ancient road from Rome, flanked by tombs. It entered the enceinte of the I st century B.C. (see plan) by a gate still preserved. This wall enclosed an irregular area far larger than that of the 4th century fort, extending dow._ to the ancient coast line and the
continuation of the road forms the main street of the town. A considerable part of it had porticoes on each side. On the right (N.) are some small well-preserved thermae, and the barracks of the firemen (vigiles), a special cohort of whom was stationed here. On one side of the central courtyard of the latter building is a chapel with inscribed pedestals for imperial statues (2nd and 3rd century A.D.) and a well-preserved black and white mosaic representing a sacrifice.
To the south-west is the theatre, an area 265 ft. square sur rounded by colonnades, in which were placed the offices of the various collegia or guilds of boatmen, raf tmen and others, which had a special importance at Ostia; the names of the guilds may still be read in inscriptions in the mosaic pavements of the cham bers. In the centre of the area are the substructions of a temple, and on the south-east side are the remains of the theatre, built in the early imperial period, restored by Septimius Severus in 196 '97 and again in the 4th or 5th century. To the south-west of the theatre are the remains of four small temples, one dedicated to Venus, and a well-preserved Mithraeum, with mosaics represent ing the seven planets, etc. To the south-west again is the con spicuous brick cella of a lofty temple, on arched substructures, hitherto supposed to be that of Vulcan, but more probably the Capitolium or temple of Jupiter, Juno and Minerva, with a threshhold block of africano (Euboean) marble over 15 ft. long; from it a street over 20 ft. wide leads north-west to the river. It is flanked on each side by well-preserved warehouses, another group of which, surrounding a large court, lies to the south west. Further still are the well-preserved Horrea Epaphroditiana et Epagathiana, a large private warehouse. Hence an ancient road, leading between warehouses (into which the Tiber is en croaching), in one room of which a number of well-preserved large jars may be seen embedded in the floor, runs close to the river to a large private house with thermae, in which fine mosaics were found : it (groundlessly) bears the name of "imperial pal ace." Farther to the south-west are remains of other warehouses, and (possibly) of the docks—long narrow chambers, which may have served to contain ships. The mediaeval Torre Bocacciana marked approximately the mouth of the river in Roman times.
The south-eastern portion of the city has been excavated only partially. Opposite the Capitolium is the Forum, with remains of a temple of Rome and Augustus, a basilica (much destroyed by mediaeval plunderers), the curia, etc. To the south-west of this are the remains of the temple of Cybele, with a portico. This lay close to the commencement of the Via Severiana (see SEVERIANA, VIA), and the line of tombs which flanked it soon begins. Farther south-east, a line of sand dunes, covering the ruins of ancient villas, marks the coast line of the Roman period.
(T. A.)