The small church of San Proto, which houses the stone tombs of the saints Crisogono and Proto, was partially investigated in 1960-61 by Mario Mirabella Roberti, professor of Christian Archaeology at Trieste University. The results were notable and brought to light the structures of a small _aula_, datable to the 4th century A.D. This structure housed the cult of one of the martyrs from Aquileia killed during Diocletian’s persecutions in 304 A.D., that is San Proto who was the pedagogue of the three brothers Canzio, Canziano and Canzianilla. The basilica which was built in the area of the present parish church was dedicated to them. The basilica was also excavated by Mirabella Roberti in the 1960s. At San Proto, Mirabella Roberti’s investigations were preceded by those of an orthodox priest, father Timotheos, who in 1950 had conducted excavations, unfortunately badly documented, in the area outside the church. He brought to light a mosaic pavement which was later in date (5th century) than that uncovered by Mirabella Roberti. Therefore, this is an area of great historical and archaeological interest, not only for the Early Christian remains but also for those of Roman date that have been repeatedly noted in this zone, which is thought to be adjacent to the ancient road from Aquileia to Trieste. The excavations were concentrated in the central part of the building and uncovered a series of floors relating to the late medieval church, in relation to which without grave goods were identified. One was a male individual buried in an earth grave whose position in the central part of the church denotes privilege. Beside this was the earth grave of a newborn baby, placed inside a cup with another cup used as a lid. A further two burials belonged to this same late medieval funerary context, identified by the 1960s excavations, but only investigated during this campaign. Of the two graves, aligned along the south perimeter, only one contained an articulated skeleton. This was a female individual, buried inside a wooden coffin, with a cloth band on the head and circular iron shoe buckles, an accessory in use between the 14th and 16th century.

The main aim of the second campaign inside the church of San Proto was the continuation of the stratigraphic excavation in the building’s central sector. In the apse area the 18th century altar was removed, revealing one of earlier date, in phase with the floor of terracotta tiles belonging to the sixteenth century phase. The earlier altar was a stone structure, probably built with reused material, with a hole in the top for the deposition of relics. The excavation uncovered a fourth burial at the north-western edge of the church. This was a wooden coffin placed in an earth grave with similar characteristics to the other three tombs investigated in 2009. Three of the tombs were on the same alignment but tomb 1 was in a central, privileged, position in a simple earth grave without a wooden coffin. These burials containing no grave goods but only artefacts relating to the clothing, document the cemetery use of the church in the late medieval period. The investigations showed that this was not a general practice but involved a restricted area within the church and was probably limited to certain individuals, perhaps members of a family linked to the construction of the church in the 15th century. The late medieval church had a simple rectangular plan (the apse area has yet to be fully investigated) and a very modest beaten-earth floor. The excavation showed that the church stood on the abandonment levels of the Early Christian basilica, attested by dumps of rubble (mortar, opus signinum, mosaic tesserae, stone blocks, tiles). The rubble had been used to fill the robbing trenches in the earlier structures relating to the 4th-5th century complex. No evidence of intermediate occupation was present in the stratigraphic sequence, although at the moment it cannot be excluded that the late medieval construction damaged the original stratigraphy. One of the robber trenches was seen to relate to a wall which must have joined the wall traditionally interpreted as the northern perimeter of the “memoria di San Proto”, in phase with the mosaic floor of the same late antique building (excavated in the 1960s). This would suggest that the Early Christian complex covered a much larger area. Its occupation phases are attested by pottery datable to between the 4th-6th century A.D.