The Pecile-type Portico of Terracina: Architectural and Functional Hypotheses on a Monumental Portico of the Imperial Period

The so-called “Pecile-type portico” of Terracina, identified by Giuseppe Lugli in 1926, is a linear opus mixtum structure whose northern wall was traced by Lugli for almost two hundred metres. The monument comprises two corridors approximately 5.60 m wide, separated by a median wall and terminating at the eastern end in a semicircular head. The monument is known through Lugli’s description, archaeological test trenches carried out by Lugli himself, and a surviving masonry stretch documented by Malizia (2024), together with a low masonry wall along Via Silvio Pellico inspected by the author and interpreted here only hypothetically. The structure has never been investigated through extensive excavation or a systematic modern survey. The study distinguishes, at a preliminary level, between documented evidence, plausible inferences, and conjectural reconstructions, adopting an explicit epistemic vocabulary based on three levels: documented, plausible, and conjectural. Measurements are examined through a metrological analysis with declared tolerances. The corridor widths, approximately 5.60 m, are analysed in relation to Roman metrology without assuming that they necessarily imply a unique dimensional solution. Likewise, the documented length is not treated as a certain design measurement. A hypothetical dimensional model derived by analogy from Vitruvius provides only approximate orders of magnitude for columns and intercolumniations and does not permit a reconstruction of the elevation. Several functional hypotheses are also formulated and compared, including a public ambulatio, a portico associated with a residential complex, a gymnasium-related space, a garden-hippodrome interpretation, and a structure serving ancillary functions. The study reaches an intentionally open conclusion: the principal functional hypotheses remain plausible but cannot be definitively discriminated on the basis of the evidence currently available. The paper therefore concludes with explicit criteria for verification and falsification and proposes a research programme involving archival research, geophysical prospection, targeted archaeological sondages, and three-dimensional documentation, aimed at reducing uncertainty concerning the monument’s plan, chronology, and function.