At the intersection of the transept you can admire another masterpiece of Andrea Pozzo. After abandoning the project of Sasso to build a true dome, the Company commissioned the painter to create a fake dome. The Well for this undertaking not resorted to the method of “grills” (as in the vault of the nave), but worked on a canvas, to be fixed in the space left blank. This solution was undoubtedly inspired by the scenes painted on cloth by the artist for the machines of the “Forty” (the practice of Eucharistic adoration that lasted precisely 40 hours). The basic idea of the work consists in having moved the vanishing point toward the nave vault so that the visitor, advancing in the church, focusing attention on the effect of fake prospective architecture. Aware of the result achieved, the Pozzo wanted to leave his students-collaborators a number of prospective studies on the dome, admired, was often imitated. The original painting, completed in 1685, was destroyed by fire; in 1823 was reproduced faithfully by Francesco Manno based on drawings and studies left by Pozzo.