The choice of sculpture as a means of communication was reiterated in the Bell Tower program with the sixteen larger-than-life statues and fifty-four reliefs shown in the adjacent gallery, of which the first and most consistent part was realised starting in 1334 by Andrea Pisano with several assistants, among whom his son Nino. The themes are divinely inspired prophecy, evoked in the figures of the prophets of Israel and the pagan sibyls, and human creativity, illustrated in the reliefs showing the biblical inventors of agriculture, sheepherding, artistic and professional work. Still other reliefs evoke astrological influences, the theological and cardinal virtues, academic studies and the seven sacraments of the Church.
The reliefs are shown in their original order, beginning on west front of the Bell Tower and moving to the south, the east, and finally the north. The hexagonal scenes of professional activities are arranged beneath the diamond-shaped ones that illustrate the “systems” structuring human life. By contrast the order of the statues, already modified in 1464, reproduces that of each side of the Tower but reorders sides in order to place the well known 15th-century figures at the center of the gallery.