The inscription on the episcopal throne states that this is the first church in Rome dedicated to Mary, mother of Jesus, although some claim that privilege belongs to the Basilica di Santa Maria Maggiore. It is certainly one of the oldest churches in the city. A Christian house-church was founded here about 220 by Pope Saint Callixtus I on the site of the Taberna meritoria, a refuge for retired soldiers. The area was made available for Christian use by Emperor Alexander Severus when he settled a dispute between the Christians and tavern-keepers, saying, according to the Liber Pontificalis "I prefer that it should belong to those who honor God, whatever be their form of worship." In 340, when Pope Julius I rebuilt the titulus Callixti on a larger scale, it became the titulus Iulii in commemoration of his patronage and one of the original 25 parishes in Rome. The church underwent two restorations in the fifth and eighth centuries and in 1140-43 it was re-erected on its old foundations under Pope Innocent II. Innocent II razed the church along with the recently completed tomb of the Antipope Anacletus II, his former rival. Innocent II arranged for his own burial on the spot formerly occupied by the tomb. The richly carved Ionic capitals reused along its nave were taken either from the ruins of the Baths of Caracalla or the nearby Temple of Isis on the Janiculum. When scholarship during the 19th century identified the faces in their carved decoration as Isis, Serapis and Harpocrates, a restoration under Pius IX in 1870 hammered off the offending faces. The predecessor of the present church was probably built in the early fourth century and that church was itself the successor to one of the tituli, Early Christian basilicas ascribed to a patron and perhaps literally inscribed with his name. Although nothing remains to establish with certainty where any of the public Christian edifices of Rome before the time of Constantine the Great were situated, the basilica on this site was known as Titulus Callisti, based on a legend in the Liber Pontificalis, which ascribed the earliest church here to a foundation by Pope Callixtus I, whose remains, translated to the new structure, are preserved under the altar. The inscriptions found in Santa Maria in Trastevere, a valuable resource illustrating the history of the Basilica, were collected and published by Vincenzo Forcella.
Interior
The present nave preserves its original basilica plan and stands on the earlier foundations. The 22 granite columns with Ionic and Corinthian capitals that separate the nave from the aisles came from the ruins of the Baths of Caracalla, as did the lintel of the entrance door. Inside the church are a number of 12th and late 13th-century mosaics. Below are mosaics on the subject of the Life of the Virgin by Pietro Cavallini. Above is the mosaic representation of the "Coronation of the Virgin". The "Coronation of the Virgin" sits atop an apse vault, and depicts Pope Innocent II holding a model of the church. Domenichino's octagonal ceiling painting, Assumption of the Virgin fits in the coffered ceiling setting that he designed. The fifth chapel to the left is the Avila Chapel designed by Antonio Gherardi. This, and his Chapel of S. Cecilia in San Carlo ai Catinari are two of the most architecturally inventive chapels of the late-17th century in Rome. The lower order of the chapel is fairly dark and employs Borromini-like forms. In the dome, there is an opening or oculus from which four putti emerge to carry a central tempietto, all of which frames a light-filled chamber above, illuminated by windows not visible from below. The church keeps a relic of Saint Apollonia, her head, as well as a portion of the Holy Sponge. Among those buried in the church are Pope Callixtus I, Pope Innocent II, Antipope Anacletus II, Cardinal Philippe of Alençon and Cardinal Lorenzo Campeggio.
Exterior
The Romanesque campanile is from the 12th century. Near the top, a niche protects a mosaic of the Madonna and Child. The mosaics on the façade are believed to be from the 12th century. They depict the Madonna enthroned and suckling the Child, flanked by 10 women holding lamps. This image on the façade showing Mary nursing Jesus is an early example of a popular late-medieval and renaissance type of image of the Virgin. The motif itself originated much earlier, with significant seventh-century Coptic examples at Wadi Natrun in Egypt. The façade of the church was restored in 1702 by Carlo Fontana, who replaced the ancient porch with a sloping tiled roof — seen in Falda's view above — with the present classicizing one. The octagonal fountain in the piazza in front of the church, which already appears in a map of 1472, was restored by Carlo Fontana.
The titulus
Ancient sources maintain that the titulus S. Mariae was established by Pope Alexander I around 112. Later traditions give the names of the early patrons of the tituli and have retrospectively assigned them the title of cardinal: thus at that time, the cardinal-patron of this basilica, these traditions assert, would have been Saint Calepodius. Pope Callixtus I confirmed the titulus in 221; to honor him it was changed into Ss. Callisti et Iuliani; it was renamed S. Mariae trans Tiberim by Innocent II. By the 12th century, cardinal deacons as well as the presbyters had long been dispensed from personal service at the tituli. Among the past cardinal priests holding the honorary titulus of Santa Maria in Trastevere have been James Gibbons, Pope Leo XII, Józef Glemp, and Cardinal Henry Benedict Stuart, whose coat of arms, topped by a crown rather than a galero, is visible over the screen to the right of the altar. The incumbent titular holder is Carlos Osoro SierraArchbishop of Madrid since November 19, 2016 upon the death of Loris Francesco Capovilla, the oldest living cardinal at the time of his death on 26 May 2016.
