Piranesi's variations on the Aurelian Wall of Rome in his four generations of the Campo Marzio were chosen as our site for a critical urban intervention. The overlapping of the four Walls created a Zone which we then superimposed with three different time periods of Rome (17th, 18th and 19th centuries). Thus the zone acquired both an external criticality, of collapsed time and space, and an internal one of its inherent formal qualities of fluctuation.