The new basilica has maintained the original 4th century plan, with one nave and four aisles. It is 131.66 meters (432.0 ft) long, 65 meters (213 ft) wide, and 29.70 meters (97.4 ft) high, the second largest in Rome. The basilica is on a T-shaped plan and aligned from west to east. There is a long nave with aisles, and this has ten bays with a half-bay at each end. Then comes a very wide transept, backed by a semi-circular apse. Flanking the apse are four external side-chapels, and a further two chapels occupy the ends of the transepts.