The restorations in 1588 by Francesco da Volterra give the basilica a large part of its present-day appearance. The simple flat wooden nave ceiling was replaced with a barrel vault, the nave pillars were opened up to reveal the ancient columns within and the ceiling of the transept was replaced by an elliptical dome. This latter was one of the first in Rome. Also the aisles were sectioned by blocking walls to create a series of side chapels; the left aisle had three arches left open, but the right aisle was completely blocked.