This chapel was built during the 17C as an oratory for the Black Penitents, a confraternity dedicated to helping the poor and sick and burying the dead. Its remarkable painted ceiling depicts religious scenes. At the centre is the cross as it appeared to the Emperor Constantine (represented kneeling), adopted by the order as their symbol. Elsewhere are depicted Constantine's mother Helena and the Twelve Apostles. The chapel has a sumptuous 18C altarpiece in painted wood.