Discover Ostia Antica

Ostia Antica is the ancient Roman city of Ostia, the port at the mouth of the Tiber 25 km south-west of Rome. Silt from the river has since moved the coastline, so the site now lies 3 km from the sea. After the city was abandoned, sand dunes covered it and preserved it -- to a degree the source puts behind only Pompeii and Herculaneum. What survives is a working Roman town: apartment blocks, warehouses, baths, bars, frescoes and mosaics, showing a kind of urbanism that is no longer legible inside Rome itself.

The republican castrum at the core has the standard rectangular plan: the cardo and the decumanus maximus cross at right angles and leave through four gates, with the decumanus carrying the line of the Via Ostiense in from Rome. Its walls are just over 1.5 m thick, built in square blocks of Fidene tuff laid irregularly, and stretches of them were later swallowed by the buildings that grew against them -- the Small Market, the Horrea Epagathiana and a row of taverns all reuse castrum wall as back wall.

Outside the gates the grid stops. South of the southern gate the cardo turns southwest onto the old coastal road to Laurentum; just past the western gate the decumanus swings southeast towards what was then a nearby beach. The city expanded along those two bends rather than on the grid, which is why the wider plan looks disorderly next to the tidy core. A third important street, the Via Semita dei Cippi, ran from the decumanus to the Laurentina gate and took its name from the cippi marking the grain warehouses.

The city walls were begun in 63 BC under Cicero's consulate and finished by Publius Clodius Pulcher, tribune of the plebs in 58 BC, in tuff from Monteverde. They enclose roughly 69 hectares on an irregular line. Their defensive role did not last: buildings leaned against them from the Augustan age, Vespasian used them to carry an aqueduct, and when late antique Ostia came under attack the walls were not restored -- the theatre was used as a fortress instead.

Three gates survive under modern names. The Porta Romana closed the eastern end of the decumanus, flanked by two square towers and rebuilt higher in the Domitianic era with marble decoration and a statue of Minerva as winged Victory. The Porta Laurentina, at the southern end of the cardo, is a rectangular tuff structure between towers 5.85 m high that still has the grooves for its portcullis. The Porta Marina faced the beach at the western end of the decumanus; it was levelled in the 1st century and replaced by an arch further south.

Ostia is built in brick and tuff, and that is the point of it. The castrum walls use square blocks of Fidene tuff; the 63 BC circuit uses Monteverde tuff in recessed bands about two feet high, roughly 1.5 m thick at the base and backed on the inside by an embankment. Above that level the imperial city is overwhelmingly brick-faced concrete, which is what let it be built upwards.

The insulae are the clearest demonstration. These are multi-storey blocks divided into apartments, with shops opening onto the street at ground level, often behind a portico. Cheaper upper-floor flats were reached by separate stairs entered from outside, so a building could be let in independent layers; the better apartments had internal staircases instead. Shops frequently carried a mezzanine on an internal stair, lit by a window above the door, used either as the shopkeeper's lodging or as storage. The Basilical House shows the logic carried further, with a bridge crossing the internal courtyard at first-floor level to make a covered central passage.

The city kept rebuilding on itself. The forum was laid out under Augustus and remade under Hadrian, who twice held the office of duumvir; construction continued to the end of the Severan age, when the theatre was restored and the Via Severiana laid out. In late antiquity the method changes again: luxurious houses were adapted out of earlier ones and faced with marble and opus sectile, often reusing older material rather than quarrying new.

How is Ostia Antica different from Pompeii?

Preservation and character. The source ranks Ostia's state of preservation behind only Pompeii and Herculaneum, but Ostia was a working port rather than a provincial resort town, and it was abandoned gradually rather than buried in a day. The result is a city of apartment blocks, warehouses and bars rather than villas.

Is the site by the sea?

Not any more. Ostia stood at the mouth of the Tiber, but silt from the river has moved the coastline, and the site now lies about 3 km from the sea.

How much of the ancient city can I see?

It has been estimated that two-thirds of the ancient town is still unexcavated. The walls enclose roughly 69 hectares, and what is open is substantial, but a large part of Ostia remains underground.

Is there a museum on site?

Yes. Finds from the excavations are housed on site in the Museo Ostiense.

What are the Mithraea?

Sanctuaries of the cult of Mithras. Eighteen have been found at Ostia, which is a direct measure of how widespread the cult was in the port's population.

Is there really a synagogue?

Yes -- the Ostia Synagogue is the earliest synagogue yet identified in Europe. Analysis of its masonry and plan indicates it was purpose-built and monumental from its earliest phase, probably in the late 1st century AD, and it was altered several times between the 2nd and 4th centuries.

Why did Ostia decline?

Its harbour was small, so Claudius built a new one at Portus and Trajan added a hexagonal basin finished in 113 AD. Economic activity shifted to Portus, and the third-century crisis cut the population. Recent excavation shows the town kept going as a wealthy residential centre rather than collapsing outright; after the fall of the Western Empire the remaining inhabitants moved to Gregoriopolis nearby.

How long should I allow?

Plan on a half day at least. The site is a street plan rather than a single monument, the walking is on ancient surfaces, and the on-site museum needs time of its own.