Tradition has it that the basilica was founded by pope Callixtus I on the spot where oil sprang from the ground, and completed by Julius I. What you see today, however, is the twelfth-century rebuilding: Innocent II had it made anew from 1138, partly with material taken from the Baths of Caracalla, that is with the pieces of a Roman bathing complex. The pope died before the work was finished, but he left the money so that it could go on.
What to see
The apse. In the semi-dome Christ crowns the Virgin, and the two of them sit on the same throne, which is not a usual way of showing them. On the left is Innocent II holding the model of the basilica: the man who paid, portrayed together with what he paid for. On the great arch stand the prophets Jeremiah and Isaiah, the symbols of the four evangelists and the seven candlesticks of the Apocalypse, with a golden cross between the alpha and the omega. Below, twelve sheep for the apostles and the Lamb.
Visiting
Beneath the older mosaic runs a band of Stories of the Virgin that Pietro Cavallini signed in 1291, and it is worth looking at the two parts one after the other: above, the Byzantine manner; below, a new sensibility, attentive to the solidity of bodies. Two ways of making mosaic on the same wall, a century and a half apart. Outside, high on the front, is another mosaic, of the thirteenth century: Mary enthroned nursing the Child, flanked by ten women holding lamps. And in a niche at the top of the romanesque bell tower a Madonna and Child is tucked away.
Our editors' tip
There is a hypothesis, by Ernst Kitzinger, that would explain the apse mosaic. In the Middle Ages, on the night of the Assumption, a great procession was held in Rome: the acheiropoieton image of the Saviour was carried from the Lateran to Santa Maria Maggiore, before the Salus populi romani, almost an embrace between mother and son. The two central figures of the mosaic hold scrolls with passages from the Song of Songs, and during that procession sections of exactly that book were sung. If the hypothesis holds, that semi-dome does not portray a heavenly scene but a Roman night, fixed on a wall.