Placido Costanzi made this modello, or presentation sketch, in preparation for an apse fresco in a Roman church. He may have shown this highly finished oil study to his patrons for approval before embarking on the actual architectural decoration. Costanzi incorporated the curving ribs of the apse, which would have been carved or molded gilt plaster in the church itself, into the ornamental decoration as a frame for the Virgin.
Above an elaborate sunburst with her monogram, the Virgin Mary dominates the central panel. Saint Luke, holding a scroll that reads " Ecce Virgo" or "Behold the Virgin," occupies the left panel, and Saint John the Evangelist looks up at her from the right. Costanzi used the typical light palette, weightless putti and angels, and artificial sky of Italian Rococo architectural decorators.