Two rock tombs side by side in a burial chamber are to be found in te very centre nave ; they have been said to house the remains of two men whose martyrdom gave rise to the creation of the religious site.
15 - Our lady of Confession
16 - Sarcophagus of St Cassien"
First half 5th century (uncertain), currently used as an altar.
The plain architectural setting comprises five compartments flanked by smooth pilasters supporting ogee arches. The central figure is that of an adolescent praying as, from the two neighbouring compartments, an older person gestures respectfully towards him. This gesture is repeated by the young mal on the far right, while in the corresponding arcade on the left is a couple, with the male figure holding up a child.