Santa Maria della Febbre was an ancient Roman mausoleum, converted into a church, just south of San Pietro in Vaticano. As a building it was older than the Constantinian Basilica. The site now lies under the Sacristy. There is a picture of it on Wikimedia Commons. 
It had a twin just to the west, Santa Petronilla, and it is convenient to discuss them together
In the 1st century AD, the area of the Vatican was dominated by a circus or ancient Roman race-track which was laid out on an east-west axis just south of the present basilica. It seems to have been a private enterprise, like the Circus Maxentii on the Via Appia, and was attached to the Villa Agrippinae which was sited where the Ospedale di Santo Spirito is now. The villa belonged to Agrippina Major, the mother of the emperor Caligula, and when he began his reign he had the circus constructed as a personal initiative and founded annual Games there in her memory. Nero apparently either finished or restored the circus, hence it is named after either emperor.
Its great landmark was the obelisk, brought from Alexandria in Egypt and set up on the spina of the circus (the central axis around which the U-shaped race-track ran).
Different historical plans of various dates show the circus having various sizes and oriented in either direction. A section of curved wall excavated on the Via di Santo Uffizio beyond the Piazza di San Pietro indicates that it was much longer than previously thought. The starting gates were probably at the west end of the basilica, although this is debated.
The presence of the circus had led to some arguing that the two mausolea under consideration were Papal structures associated with the basilica, since they were built within the circus precincts. However, the archaeologist Castegnoli investigated the buried foundations of Santa Maria della Febbre in 1957, and found stamped bricks dating the edifice to the reign of the emperor Caracalla. It was built just west of the obelisk, was aligned with the spina but its major axis was just south of it. This is conclusive proof that the circus had fallen into disuse by this period.
It is entirely unknown who was buried here although, since the property belonged to the emperor, those buried here must have been of the imperial family or to have been very close to it.
Initially, the mausoleum was a domed cylinder, rather tall. The infill needed to level the site for the basilica buried ten metres of its height, and as a result this portion of the structure was packed with rubble. The portion left above ground was rebuilt, to match in style the new Honorian Mausoleum being built just to the west.
The second mausoleum, later the church of Santa Petronilla, was constructed as part of the building project that led to the Constantinian Basilica. Previously it was mistakenly thought that it had been added by the emperor Honorius for himself and his family, hence the name.
Proof that it was not earlier than the emperor Constantine is given by its alignment; it was attached to the south end of the transept of the basilica, with its major axis continuing that of the transept. Further, its transverse axis was the same as the major axis of the Severan Mausoleum. In fact, it seems that its size was selected so that it would align simultaneously with both buildings; it is slightly smaller than the Severan Mausoleum as a result. The published claim that the footing of this edifice was also Severan would mean that it already aligned with the Tomb of St Peter when it was built at the end of the 2nd century -a claim with ramified implications.
Rather than Honorius, it is now suggested that the original occupant of this mausoleum was Anastasia, the half-sister of Constantine. Honorius and later Western emperors, together with their families, used the two mausolea as their burial places in the 5th century. The Chronicle of Prosper of Aquitaine relates that emperor Honorius was buried in a mausoleum "next to the apostle Peter" in 423, and that the emperor Theodosius II (who reigned in Constantinople) was also so buried in 450. It is known that Maria, wife of Honorius, was buried in this mausoleum in 405 since her body was discovered in 1544; whether emperors in the West later than Honorius were also buried here is uncertain.
Relationship with the basilicaEdit
The Constantinian rebuilding of the Severan Mausoleum entailed building a new apsidal porch on its west side (that is, a transverse rectangle with an apse at each end). The Honorian Mausoleum was attached to the south end of the basilica's transept by a porch in an identical style, with the transept wall also forming the north wall of the porch. A passage led from the west hand side of the Severan porch to the east apse of the Honorian porch, via a little rotunda. This passage gave access to the Severan Mausoleum from the basilica.
Rotunda of St AndrewEdit
Pope Symmachus (498-514) converted the Severan Mausoleum into a church, the Rotunda Sancti Andreae, which was dedicated to St Andrew the Apostle. Despite modern historians thinking that the Roman Empire in the West had ceased in 476, the citizens of Rome continued to recognize the authority of the emperor in Constantinople for a further three hundred years. The permission of the emperor would have been needed for this conversion, and the fact that St Andrew was the patron of Constantinople might have had something to do with it.
The pope also founded a monastery to serve the church, and also to take part in the liturgical celebrations in the basilica. As such, it was one of several in the vicinity of the basilica having this function. Unlike at the Lateran, these monasteries together did not evolve in the early Middle Ages into a community of Canons Regular , but into a Chapter of secular priests.
Church of Santa Maria della FebbeEdit
The church of St Andrew was re-dedicated to the Blessed Virgin Mary in the 14th century. An icon of her, under the title of Our Lady of the Fever, was venerated here. The fever concerned was malaria, which was a serious threat to the health of the city's inhabitants from the time of its foundation to the late 19th century.
The devotion survives in other places in Italy, notably at Tivoli near Rome which has a church dedicated under this title.
In 1450, the church was re-ordered as the sacristy of the basilica, a rôle it played for about a hundred and eighty years. Either then or before, the entrance arrangements were altered. Instead of the narrow passageway from Sant'Angelo, a broad corridor was run due south from Santa Petronilla into the entrance, with two rooms on each side and an altar dedicated to St John Chrysostom halfway along it. The entrance portico of the Severan Mausoleum was demolished.
Certain scholars whose Italian is not very good have imagined that Febbe is feminine plural, and hence have referred to the church as Santa Maria delle Febbe. It is useful to bear this in mind when making online searches.
Church of Santa PetronillaEdit
This saint has had an ancient cultus in Rome, dating from the 4th century at least, although her developed legend making her a daughter of St Peter is worthless. She was originally enshrined at the Basilica of St Domitilla in the catacombs of the same name near the Via Ardeatina, together with SS Nereus and Achilleus although she was not associated with them.
Pope Stephen III (752-7) transferred her relics from the catacomb to the Honorian Mausoleum, which was consecrated as a church in her honour in 757 by his successor, Paul I. The latter commissioned a fresco cycle depicting the life and actions of the emperor Constantine, but this was destroyed in 1463 before the edifice was demolished in the first decade of the 16th century.
It became the first national church of France subsequently, being known in the Middle Ages as the Cappella Regum Franciae and having the French kings responsible for its upkeep. King Louis XI paid for a restoration in 1471, and three years later the original sarcopagus of precious marble was found that had been used to enshrine St Petronilla in 757. It had an inscription: Aur[eliae] Petronillae fil[iae] dulcissimae ([This belongs to] Aurelia Petronilla, a very sweet girl).
A hole was knocked in the east wall to provide a new access to Santa Maria della Febbe in 1450.
Church of Sant'Angelo in VaticanoEdit
The porch of the Honorian Mausoleum was consecrated as a separate church, dedicated to St Michael the Archangel. It had a single entrance off the south end of the transept of the basilica, and one had to pass through it to get to the churches of Sant'Andrea and Santa Petronilla.
As Armellini describes, Imperial burials were discovered below the floor of Santa Petronilla three times, and (as he indignantly recounts) destroyed for their precious metal content.
The first was in 1458, when excavations for a burial of a canon revealed a fine marble tomb slab, below which were two chests of cypress covered in silver plates, one large (the coffin?) and one small. The actual bones were wrapped in cloth-of-gold. The metal was recovered for the papal mint, where it was turned into coins.
The second was in 1519, when another burial wrapped in cloth-of-gold was found in an underground arched niche.
The most tragic was in 1544, after the mausoleum had been demolished for the new basilica and its foundations were being dug out. It was the burial of the empress Maria, and contained a massive treasure. If the fairly detailed description that Armellini quotes is accurate, her corpse was wrapped in a large quantity of cloth-of-gold and was accompanied by two chests. The first, plated with silver, contained about thirty bottles and vases in gold, semi-precious stones such as agate, crystal and glass. There was a lamp in rock crystal shaped like a shell, with a cover in gold shaped like a fly. The second chest, plated with gold and silver, seems to have contained the empress's entire set of private jewellery comprising many pieces.
Everything containing metal was melted down and the profit put towards the cost of the new basilica, except one pendant which is now in the Louvre. It is a fair guess that this crass vandalism would not have occurred when Rome was at the height of the Renaissance, only twenty years before and before the Sack of Rome in 1527.
One historical question that arises is as to why a Christian empress should have been buried with grave goods, like an Egyptian pharaoh.
Destruction of Santa PetronillaEdit
As mentioned, the church of Santa Petronilla was demolished very soon after the foundation stone was laid for the new basilica in 1506. The ancient sarcophagus containing her relics had a sad end. Initially it was kept in the church of Sant'Andrea, which had become the basilica's sacristy, but was quickly moved to the Chapel of the Crucifix in the basilica. Incredibly, in 1534 the relics were removed and put into storage, and the sarcophagus was smashed up so that the marble could be used in opus sectile work in the new basilica.
St Petronilla finally came to rest when her relics were enshrined under the altar dedicated to her in the new basilica in 1606. The altarpiece is in mosaic, reproducing the original one, the Martyrdom of St Petronilla by Guercino which is now in the Capitoline Museums.
Sacristy of basilicaEdit
A sacristy is a place where the vestments of the priests celebrating in the church are kept, as well as the sacred vessels (hence the name). The old basilica seemed to have had one attached to the left hand side of its portico, but in 1450 Pope Nicholas V ordered that the old church of Sant'Andrea be converted for the purpose. The sources hint that it was not very satisfactory in its new function.
However, when the new basilica was built the old building was carefully preserved, and Michelangelo especially was keen on respecting it. A new passageway was opened to it from the Clementine Chapel on the orders of Pope Clement VIII (1592-1605), and the old entranceway from the demolished Santa Petronilla was blocked up. The corridor block from the latter with its rooms was at least partly kept, and an extension built on the east side over the former site of the obelisk.
Michaelangelo's famous Pietà was initially located here, before being moved to the Chapel of the Crucifixion.
There were several proposals for a new sacristy before the present one was built. The original scheme was for one on the north side of the new basilica, and this was provided in 1607. The result was judged not a success, and the edifice was converted into the present Blessed Sacrament Chapel in 1638. The old rotunda had to take the function of sacristy again.
Further schemes foundered on the problem of what to do with the old building, and it was not until Pope Pius VI that the decision was taken to demolish. This took place in 1777, and the ground levelled for the new sacristy building which included a residence for the basilica's serving priests. However, beneath the sacristy foundations the lower part of the ancient rotunda survives.
The icon of Our Lady of the Fever was transferred to the Cappella della Sagrestia dei Beneficiati, which is off Room 2 of the Basilica Treasury in the Sacristy. There it is enshrined in a ciborium by Donatello, which used to be in the old basilica.
The altar of the Crucifixion of St Peter in the Left Transept of the basilica is near the centre of the site of the church of Santa Petronilla.
The centre of Santa Maria della Febbe lies beneath the north-east corner of the Sacristy, just south of the corridor leading to the Chapel of the Choir in the basilica.
The two rotundas had identical floorplans. Seven large arched niches led off from a central circular space between eight massive buttresses, the eighth space being taken up by the entrance. Towards the last days of the old basilica these niches were taken up by altars, except the eastern one in Santa Petronilla which was occupied by the corridor leading through to Santa Maria della Febbe.
It is known from a description by Cosimo Fiorentino, the master mason responsible for the first foundations of the new basilica, that Santa Petronilla had a crypt with eight similar recesses. It is not entirely clear if this was the case with Santa Maria della Febbe, but there must have been ten metres of structure below the present ground level before reaching the original foundations of the mausoleum. As mentioned, the theory is that was that this portion was packed with rubble when the upper part was rebuilt as part of the Constantinian building programme. In which case, there was no crypt.
Santa Petronilla is only depicted in one 15th century woodcut, which is too poor to show detail but indicates that the two rotundas were twins. Santa Maria della Febbe is shown in several surviving paintings and drawings. It was a squat cylinder (originally it would have been a tall one, before the Constantinian infill), topped with a dome. The drum of the dome had eight buttresses, in between which were eight round-headed windows. The actual dome itself was a tiled saucer.
A drawing in the British Museum shows the additions made to the structure when it became the sacristy of the new basilica; they were very messy. See "External links", below.
Armellini (pp. 738 for Sant'Andrea, 749 for Maria della Febbre, 754 for Petronilla, 758 for Sant'Angelo.)