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Sant'Agnese fuori le Mura, Basilica Costantinina

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Sant'Agnese fuori le Mura, Basilica Costantinina is an enormous ruined 4th century basilica behind the church of Santa Costanza, and is part of the palaeo-Christian funerary complex of Sant'Agnese fuori le Mura at Via Nomentana 349 in the Trieste quarter. The best view is, however, across the tennis courts to the east of Via Bressanone.


Bibliography Edit

The historical treatment of the complex given here, relies in main on a paper published in Byzantion in 1997:

Mackie, Gillian: A New Look at the Patronage of Santa Costanza, Rome.

Catacombs Edit

The catacombs here may date from the mid 3rd century, and certainly no later than the start of the Great Persecution by the emperor Diocletian and his colleagues in 303. The martyred St Agnes was buried here in the following year, and gave her name and fame to the location.

The original set of catacomb passages form a compact and rather poorly constructed system, and this hints at an original private institution later expanded.

Documentary witness to foundation Edit

There are two fundamental documentary sources for the history of the site. One is an acrostic inscription that used to exist in the apse of the church of St Agnes, and which was published by Giovanni Battista de Rossi from a manuscript transcription. He attributed the poem to Pope St Damasus (366-84). (The text is here). The second is the relevant entry in the Liber Pontificalis. Together these sources state that Constantina (c. 310-354), daughter of the emperor Constantine (272-337), requested the building of the original imperial funerary complex. If the inference is correct, the work was started by the emperor himself before he decided to make Constantinople the imperial capital in 330. The Liber goes on to allege that the complex included a baptistery in which Constantina was baptized by Pope St Sylvester (314-35), together with Constantia the emperor's sister.

If we accept this evidence, the complex was erected between 326 (the emperor's last visit to Rome) and 330. A further surmise is that the emperor intended this to be his own mausoleum, before deciding to relocate the capital of his empire to Constantinople. There is no documentary evidence for this.

Doubt has been cast on the Liber entry on the grounds of special pleading as regards the career of Pope Sylvester, and an alternative view is that the foundation of the complex was in the period 337 to about 350. This view concludes that the funerary complex was founded here by Constantina in her own right, on what had become her property after her father died.

Later Edit

The basilica Constantinina (the Latin name) was built just to the west of the entrance to the catacombs, with its own entrance façade facing it. One theory is that Pope Damasus built a separate church over the catacomb entrance in about the year 370, and that this is the ancestor of the present basilica of Sant'Agnese. The mausoleum (now church) of Santa Costanza was built as a replacement of a smaller mausoleum at about the same time, opening off the basilica on the near left hand side. This was for Constantina and her sister Helena.

Constantina has suffered from a confused historical record, unfortunately perpetuated in some scholarly guidebooks. When her mausoleum was converted into a church a foundation myth was invented which converted Constantina (not altogether a nice person) into a saint, Santa Costanza or St Constance. In the process she was confused with her aunt, the emperor's sister, who was actually named Constantia.

According to the further documentary record, "the basilica" became ruinous and was restored in the early 6th century by Pope Symmachus. It was then rebuilt by Pope Honorius I in the 7th century, and this is certainly the present church of Sant'Agnese. The question has been: What did Pope Symmachus restore?

The present consensus seems to be that it was a church erected by Pope Damasus at the earliest, and that the basilica Constantinina was never a church. If so, it was also probably ruinous in the early 6th century and stayed that way.

The site is presently used as playing fields for the nearby school of San Leone, and there is no public access

Layout -Circiform basilicasEdit

The plan of the Basilica Costantinina is that of an elongated U with an apsidal end, and a straight entrance façade which was just to the left of the present entrance of Santa Costanza (very little survives of this). This plan is known as the Basilica circense or "circus basilica", because the layout evokes that of an ancient circus.

There are five other known examples of circiform basilicas, as they are known: San Sebastiano fuori le Mura, San Lorenzo fuori le Mura, Santi Marcellino e Pietro ad Duas Lauros, Basilica Anonima della Via Ardeatina and Basilica dei Gordiani.

The resemblance to an ancient Roman circus of this mysterious group of buildings is surprisingly close. They have entrance façades which are slightly skew to the major axis of the buildings. This was not incompetent surveying, but reproduced a feature of circuses where the straight end was also skew. A race would be from this end, round the circular far end and back again, and the skew was to ensure that the racers going round the outside of the curve would travel exactly the same distance as those going round the inside.

Why the basilicas had to have this feature is utterly mysterious. It meant that those processing from one side of the façade along the aisle round the apse ambulatory and back to the other side would walk exactly the same distance if they were walking in step. What liturgical function required this? Nobody knows. Also, San Lorenzo stands out in that the skew is front left to back right whereas the others have it reversed.


What survives of the edifice is the high stone wall at the east end, forming a spectacuar apsidal curve and supported by stepped pilaster buttresses. There is a row of large square windows below the roofline.

The dimensions are impressive: 98m long and 40m wide for the putative original building.

The present church of Santa Costanza was joined to it via a porticus or entrance hall (now gone), so one had to enter the basilica and immediately turn left in order to get to it. When you take the path to that church nowadays, you are actually walking within the basilica with the site of the original façade to your left. To the right there is a set of playing fields beyond a chain-link fence with the apse looming in the distance.

An atrium, or cloister with covered walkways, has been postulated in front of the entrance frontage on slender archaeological evidence. Foundation walls have been found at the near corners of the basilica, indicating that its side walls continued beyond the entrance façade and so the atrium is postulated from these.


A puzzling edifice like the other circiform basilicas, the structure here has gone through several interpretations and, as mentioned, it is presently doubted that it was actually a church.

Before the first serious archaeological excavation in 1954-5, it was thought that the historical references quoted were to the present church of Sant'Agnese, and that the ruin was merely a curtain wall of the surface cemetery (with the catacombs stretching out underneath). However, that excavation found foundations and evidence of an arcade of brick arches within and parallel to the exterior wall. This was interpreted as belonging to an enormous church, with an ambulatory continuing the aisles around the apse as is familiar in some northern European mediaeval cathedrals, and this became the received view. The present church would then be a new building on a fresh site by Pope Honorius after this vast basilica fell into ruin.

Further excavations were carried out in 1999, when many funerary monuments were found in the putative floor area of the basilical church. More seriously, a walled structure with its own tiny apse was found within the line of the arcade, where the high altar was expected to have been. This looks like a mausoleum. There is certainly evidence of the original timber roof of the arcade, but it is now suspected that this was the only part of the edifice to have been roofed. That is, instead of a church the building was, after all, a funerary enclosure with a roofed ambulatory running around an open central area containing graves and an imperial mausoleum (originally intended for the emperor?). If this interpretation is correct, and it is still debated, then it is possible that the original basilica at San Lorenzo was also not a church and neither would any of the other four have been. The whole subject of the status and use of these large early 4th century imperial basilicas is under revisionist review.

Two other concerns not easily reconcilable with the view that these circiform structures were churches are: The lack of foundations for a proper façade. The evidence here is rather negative, but at San Sebastiano there was a more demostrable absence. Secondly, the lack of alignment between opposite nave pillars which would have supported the putative roof. This is most obvious at the Basilica dei Gordiani.

One modern church, the design of which has been influenced by this basilica is San Basilio Nuovo.

Santa Costanza Edit

The recent archaeological excavations have also revealed that the mausoleum of Santa Costanza replaced an earlier edifice on the same site. This was a little triconch (clover-leaf shaped) building attached to the side of the basilica, which has been interpreted as a mausoleum (likely) or as a baptistery (there is no evidence for this). This building was erected at the same time as the rest of the basilica. No other appended mausolea have been discovered yet, unlike at San Sebastiano fuori le Mura where there were several.

External linksEdit

Italian Wikipedia page

Archaeological description

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