The example of the Piazza San Marco in Venice will serve to illustrate the important characteristics of volumetric space. The Piazza San Marco is a large bounded space with few fixed elements inside. What gives it distinction is the character and proportion of the "floor," "walls," and "ceiling" of the space. The two rooms of the space, the Piazza and Piazzetta, share a continuous and level floor. Except for the Basilica faqade, the walls of the space are continuous planes or, in essence, simple rectangles. Again with the exception of the Basilica, the equal height and continuous cornice line of the other buildings defines the perceived ceiling, thereby bringing the blue sky down to cap the space explicitly at a more intimate scale than is usually experienced. The much studied proportional relations between floor and wall2 provide unity. The delicate filigree and solid-void contrast of the carved masonry walls provide all the richness and variety one could wish for; by imagining the space with windowless concrete walls but otherwise unaltered, it becomes evident how critical this aspect is.