Lavinium was a port city of Latium, to the south of Rome, midway between the Tiber river at Ostia and Anzio. The coastline then, as now, was a long strip of beach. Lavinium was on a hill at the southernmost edge of the "Silva Laurentina", a dense laurel forest, and the northernmost edge of the Pontine Marshes, a vast malarial tract of wetlands. The basis for the port, the only one between Ostia and Anzio, was evidently the mouth of the Numicus river.