The oldest Ostia, its name, and geology
In antiquity an extensive and unanimous tradition assigned the foundation of Ostia to Ancus Marcius, the fourth king of Rome, in power from 640 to 616 BC. This early settlement has not been located however. The oldest remains in Ostia (the walls of the Castrum) belong to the late fourth or more likely early third century BC. There has been much speculation about the location of the settlement of Ancus Marcius. It was obviously near a mouth of the Tiber. But where was this mouth in the seventh century BC?
Now, the name "Ostia" is a bit strange. There is general agreement that it should be understood as "ostium", the Latin word for the mouth of a river, in this case the Tiber. But whereas Ostia was used as feminine singular, it is neuter plural of "ostium". Eventually the Tiber would have two mouths: a natural one near Ostia, and an artificial one near Portus. This however was the situation after the digging of the Fossa Traiana, the channel to the south of Portus, by order of Claudius. Could it be that there was already more than one mouth at an earlier date?
The issue was already discussed by Festus in the later second century AD (the text unfortunately contains a gap):
| Ostiam urbem ad exitum Tiberis in mare fluentis Ancus Martius rex condidisse, et feminino appellasse vocabulo fertur; quod sive ad urbem sive ad coloniam quae postea condita est refertur. {Quod} neutrum certe plura[liter pro?] ferri non debet. | They say that Ancus Marcius founded the city of Ostia at the mouth of the Tiber where it flows into the sea, and that he gave it a feminine name; which is applied either to the city, or to the colony that was founded later. Surely the neuter [plural?] should not be used. |
| Festus, De verborum significatu 214 (edition Lindsay). | |
R.J. Patterson comments: "The Latin word os, 'mouth', forms its plural as ora. Festus is here saying that Ostia (founded at the mouth of the Tiber and clearly deriving its name from os) is properly a feminine singular noun and not a neuter plural. Many other cities in antiquity had grammatically plural names (e.g., Athenae, Puteoli, Syracusae), hence the potential for confusion. Presumably, some Latin speakers in Festus' day were incorrectly employing plural verbal and adjectival forms alongside Ostia, provoking prescriptive correction from those inclined to pedantry" (R. J. Patterson, Selections from the Lexicon of Sextus Pompeius Festus, On the Meaning of Words, Kingston, Ontario 2018, 47).
Already in 1734 Giuseppe Rocco Volpi wrote:
| Certum habemus, vel ipsa Anci Marcii, qui Ostiam urbem fundavit, aetate, duos Tiberi alveos, atque duo ostia, quibus in mare se se exonerabat, iam tunc exstitisse. | It is certain that in the very age itself of Ancus Marcius, who founded the city of Ostia, two beds of the Tiber, and two mouths, with which it discharged itself into the sea, already then existed. |
| Giuseppe Rocco Volpi, Vetus Latium, vol. 6, 1734, 139. | |
In recent decades a tremendous amount of work has been done in Ostia and Portus by geologists. They paid a lot of attention to the course of the meandering Tiber over time and to lagoons behind the dunes. One of the objectives was to collect data that could be helpful in the search for the possible location of the oldest Ostia. Ostia's somewhat problematic name also stimulated this research. A summary of the research was published by Ferréol Salomon in 2020. It seems that at the time of the foundation of the settlement of Ancus Marcius, the Tiber mouth was to the north of Ostia, perhaps about halfway the Isola Sacra. The foundation seems to have been followed by a migration of the bed and the mouth of the Tiber towards the south, to its present position. The migration ended in the fourth-third century BC, so in the period when the Castrum was built.
Click on the image to enlarge. Salomon 2020, fig. 1.
It goes without saying that the geological observations are of great importance for the archaeology and history of the area. Surely new hypotheses will be launched soon.
Towards the end of the 19th century the Italian government planned the final land reclamation of the Roman coastal belt. This activity brought about a rather strong transformation of the landscape, which hampers the reconstruction of its original features. We are fortunate that, in preparation of the reclamation project, Giovanni Amenduni, chief engineer of the special office for the reclamation of the "Agro Romano", published a series of maps of the existing landscape (Amenduni 1884). Below are two details, of the Trajanic harbour and of the area around Ostia.
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Top: the Trajanic harbour. Right: the area around Ostia. The red lines are references for geodetic measures. The top of the map is oriented towards north-east. |
The form of the Trajanic hexagon is rather degraded. The original outline was in fact restored only in the 30's of the 20th century, during its transformation into a reservoir for irrigational use. Three small ponds are visibile to the south of the hexagon. The pond to the right coincides more or less with the so-called Darsena. The other small ponds are situated outside the Trajanic complex, but within the Claudian harbour. The land use in the northern area is given on the map as agricultural (dark yellow), whereas the southern half was by then used for grazing. This contrast reflects exactly the natural boundary between the loamy Tiber soils and the dry, sandy soils of a dune belt, the latter including both dunes of Roman times and deposits related to the post-Roman coastal expansion.
The second detail shows that, towards the end of the 19th century, Ostia was reduced to small hills, hiding the Roman constructions below layers of rubble. The outline of the original town is clearly visible however. Along a main street is written "Via dei Sepolcri". A small black square near the Tiber must the Casone del Sale, a storage building for salt, built in the second half of the 16th century (it is now the Museum). Close to the borgo and castle of modern Ostia Antica one observes a typical "oxbow" lake, denoting the original Tiber course. It is the remnant of a meander that was cut off, due to natural processes, during the Tiber flood of 15 September 1557. Since then the old meander is called "Fiume Morto" (dead river). Although the crescent-shaped lake has been filled in during the land reclamation, the original depression can still be observed in some streets of modern Ostia (for example in Via S. Massimo).
Undated engraving entitled "Ostia e il suo castello". The "oxbow" lake is visible in front of the castle.
Original owned by Jan Theo Bakker.