The dome over the transept was built in 1612 during the restoration and extension works. The dome, culminating in a lantern, rests on the drum punctuated by four windows alternating with gabled niches. The interior of the dome itself has decoration of coffering and gilded panels in the same style as that in the apse conch, executed around 1850. In the pendatives are depicted the Four Evangelists, by Giovanni Battista Ricci. At the top, the image of the Eternal Father attributed to Guido Reni.