Santa Costanza is a 4th century church in Rome
, on the Via Nomentana, which runs north-east out of the city, still under its ancient name. According to the traditional view, it was built under Constantine I as a mausoleum for his daughter Constantina (also known as Constantia or Costanza) who died in 354 AD. His other daughter Helena, wife of Julian, who died in 360 AD, was also buried here. In the early Middle Ages it was dedicated as a church to Santa Costanza (Saint Constance).
The fabric of Santa Costanza survives in essentially its original form. What were probably magnificent decoratively coloured stone panels on the walls have gone, no doubt to decorate later buildings, and a few of the mosaics have had some minor damage and incorrect restoration but for the most part it stands in excellent condition as a prime example of early Christian art and architecture. It was built next to, and in connection with, the 4th century basilica of Santa Agnese or Saint Agnes, to which it was attached mid-way along the liturgical north side.
Both buildings were constructed over the earlier catacombs where Saint Agnes was buried. Only a long section of the main outer wall of the basilica survives, from the north side and the apse at the eastern end. In the 7th century the present church of Sant'Agnese Fuori le Mura
was built a few metres away, as the Constantinian basilica had decayed and was considered too large to refurbish. One key component which is missing from Santa Costanza is the art of the central dome.
But in the sixteenth-century, drawings were taken of this central dome so the artwork can be reconstructed and examined. One key component which is not missing, and is extremely valuable to both the Art and History disciplines, is the large porphyry sarcophagus of Constantina, which was moved in the Renaissance to the Vatican Museums, where it is on display. Overall, most of Santa Costanza has been preserved extremely well.
Recent excavations suggest that this was in fact the second Christian building on the site, and may be some decades later than traditionally thought, and built as a mausoleum for Constantina's sister Helena in the reign of her husband Julian the Apostate. The larger of the two porphyry sarcophagi there would belong to Helena, and the smaller to Constantina, the opposite of what has been traditionally thought.
The earlier apsed building of the 330s was probably indeed built for Constantina, but she later had to take second place to her sister; as Constantina's fame as a saintly figure continued in the Middle Ages their roles became reversed in the popular mind.
The mausoleum of Constantina was attached to the basilica of Saint Agnese in Rome. This was a common practice in Rome and can be seen the cases of other Roman churches such as the Mausoleum of Helena
(Constantine's mother, not his daughter), which was attached to the basilica of SS. Marcellino e Pietro. The church is at the side of the Via Nomentana. This is an ancient Roman road, which still exists, which runs north-east from Rome to Nomentum (Ancient Rome) or Mentana
The area was an Imperial family estate, and the sisters were both brought considerable distances to be buried there: Ammianus records that Constantina's body was brought back from Bithynia, and Helena's from Gaul (History XIV: 11, 6). Later legend considerably elaborated Constantina's devotion to Saint Agnes, but it now cannot be determined if this was a factor in the choice of location, although in general terms early Christians believed that their souls benefited from being buried close to martyrs.
The structure of Santa Costanza is centralized both in its physical structure and purpose. It has a circular ringed design and domed ceiling. It was built of brick-faced concrete. Its structure is basically two rings supported by columns placed around a vertical central axis. The upper ring sits on the columns while the "lower ring encloses a circular ambulatory whose space flows between the columns into the axial cylinder."This design essentially creates two spaces or two worlds, that of the ambulatory and that of the upper dome.
The screens of the ambulatory and inner ring create a dark contrast to the bright upper space of the dome. This contrast of light can be seen in the picture of the main interior.Twelve columns, creating twelve arches, hold up the dome which has twelve windows. This could be a reference to the twelve apostles.
This creates a central space which interplays with dark and light. Opposite the entrance in this central space there is "a kind of baldacchino...rises above a porphyry plaque which, below the middle arch of the center room, once seems to have carried the princess's sarcophagus".This is where the sarcophagus of Constantina would have rested.