Four Crowned Saints and relief at base of tabernacle

This sculptural grouping was commissioned by the Maestri di Pietra e Legname, the guild of stone and woodworkers, of which Nanni di Banco was a member. The guild's patron saints were these 3rd century Christian sculptors who were willing to die rather than carve a statue of Aesculapius for the Emperor Diocletian. There is a sense of a narrative as these four unified figures, arranged in a semi-circular group on a pedestal in an arc form, seem to engage in serious conversation
Although the two rear figures stand in front of engaged half-columns (a reminder of the Gothic tradition), still the statues look classical. The draperies look like Roman togas and the faces, in their individuality, recall Roman portrait sculpture.
The scene at the base of the tabernacle seems to depict contemporary stoneworkers (they are not in togas) doing the kind of work Florentine sculptors did: building walls, carving twisted columns, executing a capital, or carving a nude figure.