The 2015 campaign concentrated on the area occupied by buildings B and C, datable to the 5th-7th centuries.
The first, and earliest, contained a rectangular vat inside the apse (USM 314). It had a waterproof lining opus signinum and a lead pipe for draining the water it contained (US 639), positioned slightly off-centre to the north-west.
The second, certainly pre-dating the 7th century, contained a large circular vat (USM 306), also waterproofed with opus _signinum, abutting the north-west side wall of building B, reused as the foundation for the semicircular apse (USM 304-541) of building C.
Both vats drained, via two separate stone and mortar channels positioned at a right angle (USM 636, 638), towards a sump (USM 315). A coin of Leone I (a.a. 457-474), found in the drain of the circular vat in building C, dates the baptismal structure to at least the last quarter of the 5th century, and therefore also the church housing it.

As no certain attributes have been found, it is not yet possible to assert that building C was a cathedral, although it seems to coincide chronologically with the presence of bishop Quodvultdeus at Amiternum, at least as the builder of the mausoleum of the martyr Vittorino in the catacombs of the same name. However, the baptismal function of the scared space is clear. The anomalous position of the circular vat (USM 306) on the central axis of the church at the entrance to the apse (USM 304-541), raises questions about parallels with examples in Dalmatia and, in particular, North Africa. This could be taken as evidence of a specific baptismal liturgy centred on the church presbytery, which it is known was a parish church prior to the first attestation in 850, following the suppression of the bishopric, probably the consequence of the murder of bishop Ceteo by the Lombards in about 604.

In fact, there was settlement and ecclesiastical continuity at least from the 5th century until the mid 10th century and again from the mid 11th until the end of the 14th century. There was possibly a brief interruption from the years preceding the inspection by Dietrich, bishop of Metz, in about 970, until the reconstruction of building A in the 11th century.
The structures in question were damaged during the 12th century, when the entire settlement was substantially reorganised, while the abandonment and robbing phases of the entire complex can be dated to between the late 13th and the mid 14th centuries.