From times inmemorial, man has felt the need for painting, writing or scribbling on the walls. The intentions behind these drive are quite varied: used as ritual invocation for hunting or as a decorative motif; thought as a propaganda objective or just for showing discontent or selfaffirmation trough graffiti. In the history of mankind it is worth noting the times where this action enters the category of art, periods in which the parietal painting shows big capacity in order to change the perception of reality surrounding us; something we can assimilate as illusionism in art. This paper studies the means, especially the mural painting, by which the firsts permanent italian Mannerism and Early Barroc theatres attain the effect of dematerializing their limits. With its use, reinforced with certain architectural and sculptural elements, it pursued different objectives: from the academicist illusion of a comeback to a time when theatrical representations took place in the open air, in an idealized setting which evoked his classical, festive and relaxed origins, to a clear use of personal political propaganda which anticipates the theatre of absolutist goverments.