Conímbriga is one of the largest Roman towns excavated in Portugal — and the most extensively dug and best-preserved — spread across a low plateau near the village of Condeixa-a-Velha, about 16 kilometres south-west of Coimbra. The name is older than Rome's presence: it joins the pre-Roman word conim — 'a place of rocky height' — to the Celtic suffix briga, 'citadel'. People had lived on the site since the 9th century BCE, when the indigenous Conii and Castro-culture communities held the hill. When Roman armies pushed into central Lusitania around 139 BCE, Conímbriga was already a walled, built-up settlement sitting on the road that linked Olisipo (Lisbon) to Bracara Augusta (Braga) by way of Aeminium — the town that would later become Coimbra and take Conímbriga's name with it.
Under Roman rule the town flourished. Between AD 69 and 79 the emperor Vespasian raised Conímbriga to the rank of municipium, and a wave of building followed: a new forum with its basilica and temple, public baths fed by an aqueduct nearly three kilometres long, an amphitheatre, colonnaded streets and grand private houses. Judged by the seating its public buildings implied, the town held something like 10,000 people at its height. Italian colonist families — the Lucanii, the Murrii, the Vitellii — settled here and married into local Lusitanian families, and the archaeology captures that fusion in stone, glass and mosaic across three centuries of prosperity.
The two houses everyone comes for are the Casa dos Repuxos and the Casa de Cantaber. The Casa dos Repuxos — the House of the Fountains, or 'jets' — is a 2nd-century domus built around a central garden whose pools and playing water jets have been restored to run again; its floors are carpeted with some of the finest polychrome mosaics in the Iberian Peninsula, hunting scenes, the four seasons, mythological figures and geometric borders in astonishing preservation. The Casa de Cantaber, one of the largest private houses known anywhere in the western Roman Empire, sprawls across bath suites, courtyards and reception rooms. Between and around them run the shops, the streets and the great forum that make Conímbriga less a set of ruins than an actual readable town.
The most dramatic thing at Conímbriga is a wall. As the empire weakened in the late 3rd century, the townspeople threw up a massive new defensive rampart — and in their hurry they drove it straight through houses, streets and monuments, quarrying their own city for stone. It bought them time, but not enough: between 465 and 468 the Suebi sacked the town, and its people scattered. The bishop's seat moved to Aeminium — Coimbra — and Conímbriga slowly emptied, which is exactly why so much survives. It was never rebuilt over. Excavation began in earnest in the 19th century, the Monographic Museum opened on site to hold the finds, and today the ruins, the museum and the archaeological reserve are visited as one place on a single ticket.