The eastern side of the Basilica was built in a semicircular apse which Maxentius added two side chapels, on the west side, Maxentius built an atrium to the basilica and baptistery.
The eastern side of the Basilica was built in a semicircular apse, Maxentius built an atrium to the basilica and baptistery. Maxentius added two side chapels. This was on the west side this semicircular apse.