Research undertaken in 2005 in the archaeological area next to the church of Ss. Nazario and Celso at Diano Marina (IM), a nodal point in the spread of Christianity in this territory and ancient site of the Roman mansio of Lucus Bormani , continued the investigations carried out in the middle of the last century by Lamboglia. This work had identified, north of the church, a Roman structure divided into several spaces that were difficult to interpret (settling tanks, a cistern system?). Later campaigns (1959 and 1963) in the area south of the church revealed that the building had two phases, dated loosely to the late Romanesque period (14th century) and pre-Romanesque period (6th-10th century) which overlay an earlier nucleus of early medieval date which is believed to be the first religious complex dedicated to the saints Nazarius and Celsius.
The latest research identified a continuous stratigraphic sequence which runs from the Roman to the late medieval period and beyond.
The Roman period (3rd-4th century A.D.) is attested by a wall on a north-south alignment, found at the western edge of the excavation, which coincides with the continuation of the western perimeter of the large structure identified to the north of the church by Lamboglia in 1947 (interpreted at the time as a cistern or settling tank).
The structures abutting the Roman wall and a possible apsed hall, perhaps the original chapel dedicated to the saints whose cult spread in Liguria from the 5th-6th century onwards, date to the early medieval phase.
The third period is represented by the pre-Romanesque building site used for the construction of the rectangular church with a horseshoe shaped apse which overlies the other structures, and the burial in a rough stone coffin containing the remains of a disarticulated inhumation placed on top of the lower limbs of an earlier burial, seemingly in its original place, which in turn overlies two lots of skeletal remains.
The pre-Romanesque floor level was covered in the 13th-14th century (Romanesque phase), as attested by a bronze buckle. The semicircular apse which rests on the earlier building can be attributed to this period.
Between the 14th-17th century the entire area south of the Romanesque church was used as a cemetery with simple earth graves bordered by stones, the bodies placed on an E-W alignment with the head to the west. The skeletons of four adult individuals and one child were recovered. The burials were identified on the surface by stone markers and bone remains. In the 18th century the church was extended to the west. (MiBAC)