Gaulli's frescoes were a tour-de-force in illusionary painting, depicting the church's roof opens up above the viewer (and that the panorama is viewed in true perspective di sotto in su, similar to Correggio's frescoed dome ceiling depicting the "Assumption of the Virgin" or to Cortona's grand allegory at the Palazzo Barberini. Gaulli's ceiling is a masterpiece of "quadratura" (architectural illusionism) combining stuccoed and painted figures and architecture. Bernini's pupil Antonio Raggi provided the stucco figures, and from the nave floor, it is difficult to distinguish painted from stucco angels. The figural composition spill over the frame's edges which only heightens the illusion of the faithful rising miraculously toward the light above.