Of the rivers of the Roman Campagna the Numicus, perhaps, attracts especial interest, not only because of several ancient cults connected with it and its resultant peculiar sanctity for the Romans, but also because of three references to it in the Aeneid. In the seventh book, after the Trojans land on the left bank of the Tiber, they prospect the newly-discovered land, and bring back word to Aeneas
This seems to imply that the Numicus is second in importance only to the Tiber in that locality. Then an envoy is sent to Latinus, and to his questions Ilioneus, the herald, replies
Thirdly, in the Gathering of the Clans, the coastal district of Latium is summarised in the lines
Apart from the fact that in these passages the Numicus is coupled with the Tiber, and that in the last two its sanctity is manifest, little evidence can be gained from Vergil in regard to the location of the river.
Between Ostia and Antium some half-dozen streams flow over the Roman Campagna and debouch on to the shore of Latium (p. 3, fig. 1), four of which have severally been recognised by various authorities as the Numicus. About two kilometres south of the Tiber is the Canale dello Stagno, a sluggish stream which serves as a drainage canal for the tract of land, now reclaimed for tillage and pasture, which once was the Ostian lake and the site of ancient salt beds. It appears originally to have been natural but at some period to have been canalised ; for, though the course is not quite straight, the banks are trim and regular. It is wide enough to admit of a bridge with three arches (pi. iii, 1).