The site of the abandoned Roman municipium of Trea is situated in the middle valley of the River Potenza, some 30 km from the Adriatic shore.

The only remaining visible ruins are two small sections of the former city walls, partly incorporated in a now abandoned farm house.

The Roman town flourished between the reigns of Augustus and Antoninus Pius, as indicated by the large collection of funerary monuments, statuary and epigraphic evidence.

Around AD 1000 the population probably moved towards the more easily defensible hill-site of Montecchio (later called Treia) and the original town site remained practically deserted.

Montecchio eventually became part of the Papal States, and in 1790 Pope Pius VI rewarded it for its faithfulness by raising it to the official rank of "city", at the same time renaming it by its Roman name of Treia.

Roman Trea was situated along an important byroad of the via Flaminia, which connected Rome directly to the harbour city Ancona, via most of the Potenza Valley.

The town wall delimiting the main urban area has an irregular oval shape, which agrees well with the general topographic configuration of the hilly plateau.

The discovery of a marble head of Serapis and a number of smaller Egyptian statuettes, as well as the second century AD inscription[3] that mentions the temple of the “Domina” (the goddess Isis), can lead to the interpretation that this foreign cult was practiced here.