From a formalist position, urban planning can be understood as a figure/ground problem. This essay investigates two preeminent figure/ground diagrams within the history of urbanism. The first diagram, the Nolli plan, defines the ground of the city by its buildings seen as an anonymous mass, from which the figurative open spaces of circulation are carved. The second formalist diagram of the city, the Piranesi diagram, formulated for the Marte Campi project for Rome, sees the figure of the city as defined by all its architecture, and the ground is seen as the circulation spaces between buildings. It has been used to understand the modernist city, where the figure, defined as building mass, floats above a liberated ground. A materialist approach toward masterplanning views the city as an emergent effect of economic processes. Seeing all morphological formations driven by forces of money, the figure, as a building, can no longer stand as a unified entity or object. If from a materialist position the urban figure is defined as an aggregate, the ground of the city can then be seen as the matter in which these aggregations take their physical shape; the economic valuation of land is established. Two research projects will serve to exemplify this approach: a project for the former airport at Aspern in Vienna, and a project for a site in the San Fernando Valley in Los Angeles.