The 12C basilica plan of Pope Innocent II’s architects has been embellished down the centuries. Inside, while the 17C ceiling by Domenichino is impressive, the chancel mosaics are spectacular. The prophets Isaiah and Jeremiah decorating the triumphal arch date fom the 12C, as do the mosaics adorning the apse. Beneath them, Pietro Cavallini has created a masterful ensemble of scenes around the Virgin.