Il mausoleo di Costanza

The mausoleum of Costanza

The monumental complex consists of the Basilica of Saint Agnes Outside the Walls, the so-called Coemeterium Agnetiis, or Cemetery of Agnes, and the Mausoleum of Santa Costanza. The mausoleum was built around 350 A.D. for the Emperor Constantine, and his daughters Costanza and Helena, both of whom died in the second half of the 300s. It later became the baptistery of Saint Agnes, and in 1254, during the reign of Pope Alexander IV, was transformed into a church. The mausoleum is a circular building, and was originally surrounded by a portico, a rectangular atrium, and two lateral apses. The mausoleum is a circular building, and was originally surrounded by a portico, a rectangular atrium, and two lateral.

The mausoleum was once richly decorated with fourth-century mosaics, but most of these, such as those on the walls and on the central dome, have not survived. Among the surviving pieces of original artwork, we can see the mosaics on the vault of the deambulatorio and two opposing niches that open to the perimeter wall. Only the mosaics of these two niches have specifically Christian themes. They depict the Delivery of the Keys (Traditio clavium) and the Delivery of the Law (Traditio legis) to Saint Peter.

The gallery that encircles the central space has a diameter of 22.5 meters and was built with a popular technique of Roman construction. It consists of a supporting framework of brick covered in a mix of concrete, tuff, and pumice stone, which was used to prevent weighing down the structure. The interior of the barrel vault is completely decorated with mosaics.
Parts of the mosaic show scenes inspired from pagan Roman culture, and because of this, the mausoleum was for a time mistaken for a temple of the god Bacchus. A series of scenes show young people who gather, carry, and crush grapes. Although the scenes depict a pagan ritual, the illustration could also have a Christian interpretation, if taken as a reference to the Gospel passage in which Christ compares himself to a grapevine, and his followers to branches:
"Ego sum vitis vera... vos autem palmites"
"Io sono la vera vite... e voi i tralci" (John 15:1-8)

The rectangular niche across from the entrance of the mausoleum once housed the sarcophagus of Costanza. The tomb, made of red porphyry (an exclusive marble reserved for the imperial family), and decorated with harvest scenes, was later moved to the Vatican Museums. The sarcophagus of Costanza's sister Helena was perhaps also once in the niche. Helena's tomb was moved to Saint Peter's in 1606 and used to hold the relics of the Apostles Simon and Jude.