San Silvestro a Priscilla is a heavily restored small palaeochristian basilica over the original entrance to the Catacombs of Priscilla.
This is to be found in the park of the Via Ada, just south-west of the Piazza di Priscilla on the Via Salaria in the Trieste district. It should not be confused with the convent chapel of Santa Priscilla by the modern entrance, on the other side of the main road.
This church was originally erected by Pope Sylvester (314-335), over the existing burial site of the martyrs Felix and Philip in the upper level of the catacombs (the story of these alleged martyrs has been lost). The ground level was dug away to achieve this, leaving the shrine in between the apse of the basilica and its nave. Immediately in front of the entrance façade another, slightly larger apsidal building was erected, and this functioned as a mausoleum for many Christian burials attracted to the sanctitiy of the site.
The basilica itself later received the dedication of San SIlvestro after the pope, and is known by this name in pilgrimage itineraries of the early Middle Ages. It is not known when it was abandoned, but the 9th century is likely.
The archaeologist De Rossiwas the first to note the ruins, in 1890. Systematic excavation was undertaken by Orazio Marucchi in 1906, who revealed the adjacent mausoleum. Subsequently, walls and a roof were erected over the complex and an altar installed in the basilica. However, it was never re-consecrated (unlike the basilica at the catacombs Santa Domitilla, which received a similar treatment).
Access to the interior has been as part of a guided tour of the catacombs, but recently the tour seems to have excluded it at least on occasion. There has been a recent archeological investigation and restoration.
There is not much to see from the outside. The combined basilica and mausoleum is in a grassed area, but had bushes and trees growing right next to its walls until at least recently (which cannot be good for the structure).
The plan of the basilica nave is almost square, with a semi-circular apse attached as wide as the nave. The latter has a triumphal arch and a conch, and also has a wide arched recess at ground level. In this recess has been placed a so-called bishop's throne, a stone structure imitating ancient episcopal seats in other churches in Rome. Foundations were found for a pergula or altar screen under the triumphal arch, formed of slabs of marble on edge supported by low pillars. The present structure there is modern, but the two taller Corinthian pillars on either side are original and have been re-erected. There used to be a modern altar in front of the chair, but this seems to have been removed.
The walls of the basilica are used to display inscriptions recovered from the catacombs. Copies of two epigraphs by Pope Damasus are preserved, one dedicated to SS Felix and Philip and the other to Pope Marcellus (the originals were stolen). Also preserved is the base of a small column with an inscription reading Martyrum Filicis Filippi.