The city is not a work of visual art. It cannot be perceived from one point and at one time. Its mental image can evolve only as a sequence of perceptions. In this respect, it is akin to the products not of the “spatial” but of the “temporal” arts, to works of music or literature. But a symphony or a novel is the work of one mind, created in a definite span of time; once completed, it remains unchanged. Not so the city. The polis is the body politic; the ‘civitas’ is the community of its citizens, interacting in cooperation and conflict. The city is a historical process; change is its very essence. Generation after generation, individuals and groups build, alter, destroy and replace the artifacts that are the visible city.