The first documented bishop of Florence is San Zanobi (398-429), who chose San Lorenzo as his seat and made it the city's first cathedral. The spread of Christianity is based on the adherence of the faithful, but the bond with the universal Church is maintained through the apostles’ successors, namely the bishops, and the episcopal see (cathedra) becomes the point of reference for the Christians of any Diocese.
The church contains Bronzino’s fresco The martyrdom of San Lorenzo (1565-69), where the location of the martyrdom is indicated by the enormous building in the background and by the columns that act as a backdrop to the scene.
Above the altar of the third chapel, the painting San Lorenzo and the souls in Purgatory by Niccolò Lapi (eighteenth century) is significant for its mode of devotion. The saint wears the dalmatic, a liturgical vestment of the deacons, and presents himself as an intermediary between the souls of purgatory and the Trinity, which can be seen beyond the angels. The Basilica di San Lorenzo naturally became a destination for pilgrimages, its influence bolstered by the development of the neighbouring market.