In the lower town, in the large square facing the Cathedral, extends an archaeological area of great interest (around 1.000 mq.), that preserves the remains of successive chronological stratification: from the Roman road with intact stone slabs, to the remnants of Roman and Medieval buildings; from the Roman heating system via hypocaust, to a Christian Baptistry from the 11th and 12th Centuries and built to a circular plan.
After the collapse of the Roman city, in the area developed a large building of narrow and elongated shape, with oblique orientation compared to the previous plant; dated to the VIII-IX century AD, it is probably connected with the oldest episcopal seat of the city as suggested by type, size and quality of construction and the proximity to the cathedral.
The Christian Baptistery is built to a circular plan, which only the foundations are preserved, with seven pillars on the inner ring and a horseshoe-shaped apse. In later times the whole area was destined for funerary use only.
