Roman Ruins of Tróia

The Roman Ruins of Tróia occupy the northwestern side of the Tróia peninsula, on the left bank of the Sado estuary, opposite the city of Setúbal but within the territory of the Carvalhal parish (Grândola municipality, Setúbal district). Classified as a National Monument since 1910, the site corresponds to the largest known fish-salting and preservation production complex in the entire Roman world, continuously active between the 1st and 6th centuries AD.

A Factory on the Scale of the Empire

The choice of location was no accident. The Sado estuary provided shelter, abundant fish, and nearby salt deposits—three essential conditions for an industry that transformed tuna, mackerel, and other species into long-lasting preserves and the famous garum, the fermented fish-gut sauce that seasoned tables across the Mediterranean. The workshops were organized around central courtyards, flanked by series of masonry tanks lined with opus signinum—the cetariae—where fish were layered with salt.

About twenty workshops of varying sizes have been identified: the largest exceeded 1,000 m² and contained nineteen tanks, while the smallest, at 135 m², had nine. This concentration of industrial units, entirely geared toward maritime export, sets Tróia apart from simple coastal villae and justifies its interpretation as a true industrial settlement.

Tróia inverts the romantic image of Roman ruins: here, there are no temples or theaters, but rows of salting tanks—the raw testimony of an Atlantic economy driven by fish and salt.

Baths, Necropolises, and the Paleochristian Basilica

The long occupation of the site left much more than workshops. Excavations have uncovered a bath complex of about 450 m², equipped with an apodyterium, frigidarium, tepidarium, and caldarium heated by a hypocaust, with traces of mosaics and a palaestra. There is also a residential area—the so-called Rua da Princesa—a mausoleum, and necropolises with diverse funerary typologies. Late Christianity made its mark in a Paleochristian basilica with once-frescoed walls, a sign that the community survived the religious conversion of the Late Empire.

Archaeological interest in Tróia is long-standing. The first known excavations date back to the second half of the 18th century, sponsored by the then-infanta D. Maria, the future Queen Maria I; in the mid-19th century, the Lusitanian Archaeological Society revealed mosaics and painted walls; and between 1948 and 1967, campaigns exposed the baths, salting houses, necropolises, and basilica.

Tróia in the Context of Roman Lusitania

The complex is part of the dense economic network Rome established along the coast of the province of Lusitania, which includes sites studied on the Roman archaeology in Portugal page. Opposite Tróia, on the other side of the Sado, the city of Setúbal inherited the Roman name Caetobriga, with which the complex maintained close supply and market relations. In terms of scale and preservation, Tróia rivals the great Roman urban complexes of the country, such as the Roman Ruins of Conímbriga, yet it offers a rare perspective: that of a Roman industry frozen in its own workspace.