A number of theoretical forms have been suggested for the sustainable city. All are based on the notion of reducing the need for movements by private motor car, and a reduction in the transportation of goods by road. From continental European sources the compact high-density city is advocated. At another extreme are proposals for low-density decentralized urban areas. A third school of thought suggests an urban form based on policies for ‘decentralized concentration’. The fourth theoretical position develops the concept of the Sustainable City Region, extending the ideas of Howard and the Garden City Movement (Breheny and Rookwood, 1993; Elkin et al., 1991a; Howard, 1965; Owens, 1991). Authors advocating a darker green philosophy suggest that the city should be located within a largely self-sufficient region. There is also a difference amongst authors about the preferred type of detailed city structure for sustainable development. Such preferences include: linear forms, dispersed structures, centralized and polynucleated urban forms, or some variation of the grid. Despite the many theories and the strength of views held by some of the advocates, there is, at the moment, little hard evidence in terms of urban metabolic efficiency or even energy efficiency to support any of the structures unequivocally. It is not possible to state categorically that one particular theoretical urban structure is more sustainable than another. In view of the inconclusive evidence, this chapter will review the origins of the ideas for city form. In particular, it will discuss the nature of the three main metaphors which have been used as a basis for understanding and coming to terms with the city. The theme of the chapter is symbolism and the city: it will form the basis for the analysis of specific city forms in Chapter 7.