The façade, restored in 1997, is divided into two levels. The lower level features three marble portals with architraves decorated with vegetal motifs, largely built with materials from the classical era. The upper level has three large windows: the lateral ones with triangular pediments and the central one with an arch.

The interior consists of three naves, once divided by tall, fluted Doric spolia columns supporting a grand trabeation. Above this structure, the walls of the central nave were likely adorned with a stucco finish that simulated another Doric order. Towards the triumphal arch of the apse, the original trabeation elements are still visible, though over the centuries they were replaced by arches supported by pillars and columns. At the end of the naves are three apses: the lateral ones are square, while the central one is semi-circular.

The presbytery, with a square plan, is architecturally distinct from the central nave as it retains its original trabeated appearance. At each of its four corners rise pairs of tall, fluted Corinthian spolia columns, above which sections of trabeation rest. Higher up, an octagonal dome with ribs is supported by original corbels decorated in bas-relief—though its current shape may not be original.

In the centre of the apse, within a niche, a monogrammed and gemmed cross is frescoed, accompanied by traces of painted faux marble decorations, indicating the basilica’s earliest pictorial embellishments. Higher up, a 13th-century fragmentary fresco of the Madonna with Child and a Saint can be seen, alongside the 16th-century Crucifixion, attributed to the school of Lo Spagna. The walls and two small chapels house additional frescoes dating to the 14th and 15th centuries.