Together with the forum area the archaeological exploration of Rione Terra has brought to light the line of the colony’s western cardo, below the present via De Fraja. This cardo sloped slightly to the north in order to join up with the decumanus below via Duomo. It was paved with trachyte basoli, whilst the rudus was made up of a compact cement conglomerate bed containing abundant stone chippings, directly overlying the tufa bed rock. The road was delimited to the east and west by sidewalks with relative crepidines of parallelepiped trachyte blocks, bedded in cement nuclei, partly overlying the basoli and faced in patchy opus signinum.

The ancient road was flanked, in this stretch, by a series of rooms with public functions, probably tabernae.

In its latest visible layout the central stretch of the cardo was paved with lava stone basoli of various shapes and sizes. A number of buildings faced onto the road, whose entrances had piperno or marble thresholds. The eastern side was also delimited by a porticoed ambulatory with rectangular pillars of squared travertine blocks which probably supported opus latericium arches.

At the southern end, by the chapel of San Liborio, the cardo met the southernmost decumanus of the colony, which in the first stretch is below the modern via Villanova. The short stretch of uncovered road was flanked to the north by arches on opus latericium pillars, perhaps repeated on the south side. Where the two roads met there was a monumental staircase with marble steps, flanked by more pillars. Only preserved in the final part and covered by the steps leading up to San Liborio, it was reached from the cardo and faced the south side of the decumanus.