It consists of a vaulted nave and an apse. East of the crossing are four rectangular bays terminating in a semicircular apse. The dome above the apse was decorated with mosaics. Large Early Christian churches generally took the form of aisled basilicas with an apse. Cracks also appeared in the flying buttresses surrounding the apse. They were painted prior to the frescoes in the apse. The space between the eight rooms was filled with heptagonal chapels with a triangular apse. A crypt containing Celsus's sarcophagus was located beneath the floor of the apse. The tomb was centered behind the High Altar in the apse. A fresco in the apse depicts Christ Pantocrator. The mosaics in the apse are late Roman art. The altar stood in front of the apse. There is a chevette of chapels surrounding the chance apse. In December 1923, the southern apse of the cathedral collapsed. The stupa is at the center of the apse, with a circumambulation path around it.