The basilica measures 75 metres by 54 and is divided into three naves with side altars.
The central aisle, the imposing vertical dimension of which is enhanced by the golden skirting and acanthus foliage which was inserted by Martino Longhi between the cornice and the vault, thus providing an ideal prologation of the sphere of the apse. On the vault itself we notice the fresco of Giacinto Brandi, “The fall of the Angels” executed between 1677 and 1679.
|The side aisles, embellished with a chapel and cupola, are constructed in a way that they join each other in a space which includes the Tribune. On the axis of the two side-chapels to the left and the right of the Tribune, we find a transept which is crowned with the cupola at the point where it joins the central nave.|
|The decoration in gold stucco in the central aisle, in the transept and in the Tribune itself, was planned by Pietro da Cortona and executed by his best pupils, Cosimo and Giacomo Fancelli (1619-1671).(1619-1671).||The wings-spans of the smaller aisles, in perfect consonance with the chapels and the open space, constitute a perfect roman gallery of the late 16th century. The statues are the work of Francesco Cavallini sculptured between the years 1677 and 1682.|