This catacomb, which consists of two separate cores, extends over a single floor with galleries connected to the related religious building. The construction of this edifice, in the fourth century, was encouraged by Bishop Urso so as to monumentalise the burials of the martyrs Alexander, Evenzio and Teodulo, who were persecuted during the time of Diocletian.

Within the basilica are conserved two vestibule columns and, at the end of the nave, the episcopal chair; the altar is located in the middle, whereas on the floor several sepulchral inscriptions referring to the faithful and to bishops may be found. Furthermore, within the cemetery chambers are some niches carrying frescoes.