The altarpiece depicts The Martyrdom of St Justina. The altar frontal is a slab of verde antico, in which is an oculus with a bronze grille surrounded by palm branches. The triumphal arch is supported by a pair of Ionic piers in yellow Siena marble, and on the archivolt are two stucco angels holding a banner that proclaims the presence of the relics of the martyrs under the altar.