The Road Network of Lower Terracina in the Imperial Age: From the Centuriated Grid to the Via ad Portum

This paper examines, through a historical‑topographical and Roman land‑surveying approach, the organisation of the road network of lower Terracina during its phase of maximum development between the 1st century BC and the 2nd century AD. It analyses the relationship between the Roman metrological system (actus, iugerum, heredium), the orthogonal planning of the coastal settlement, and the course of the via ad Portum, the axis linking the Via Appia to the ancient harbour. The study explicitly distinguishes the urban grid of the lower city from the agrarian centuriation of the Terracina Valley described by Hyginus Gromaticus, two different and non‑overlapping systems. An original result is the detection of a 15–16° misalignment between the north‑eastern and south‑western sectors divided by the Fiumicello stream, interpreted through the model of dual coastal orientation documented in other Roman cities. The paper provides a graded critical reading of the available evidence, distinguishing between archaeologically attested data, plausible hypotheses, and working conjectures.