The inside of the Basilica retains the appearance that it probably had in the Middle Ages, in spite of the changes undergone over the centuries, especially in the 1500s. According to medieval practice, the columns and capitals are all in re-use material and come from Rome.
In the basilica is one of the oldest examples of Lucca medieval painting of the early 12th century, with the three saints Lorenzo, Vincenzo and Stefano, after whom the church was first named. The frescoes and decorations inside date from the 14th to the 19th century and, among the most prized works in one of the chapels, there stands out a polyptych (panel painting), a work by Jacopo della Quercia.
But the most important work, inseparably linked to Lucca Romanesque sculpture, is the Baptismal Font (or perhaps a Lustral Fountain), positioned at the beginning of the right-hand nave and dating from the 12th century; the work is signed "Robertus Magister".
Around the circular basin, in a convulsive motion that envelops it, is a tumult of Biblical figures, contorted and sometimes disjointed, so that the leg of one horseman seems to ride back to front. Santa Zita, very dear to Lucca, is venerated in one of the oldest chapels of the church, built over the space in the cemetery where she was buried in 1278.
Santa Zita is the patron saint of domestic servants, housewives and also bakers, because of a miracle by which she is said to have transformed bread into roses to defend herself from the accusation of having stolen it from the family where she was in service to give it to the poor. The saintly aura that already surrounded her during her lifetime was fed by the fact that her body, on being exhumed, was found completely intact.
This is probably explained by the characteristics of the ground, which is extremely rich in minerals, but this did not prevent people from talking about a miracle and now the frail body of the saint is displayed in a shrine, inside a chapel decorated with the images of her life.