With the considerable and continuous attention of individual, academics, and governments to the issue of environmental sustainability, in the three late decades of the 20th century, the demands for ‘sustainable urban development’ and sustainable cities seem to be the most pressing challenge facing humanity in the twenty-first century.
On the other hand, the search for the ideal city, the city form that would be able to express both the advantages of modem technology and the soul of rustic life, on the basis of enlightened ideas of social justice, has long been a major concern to many philosophers, social reformers, writers, and architects and planners. This search, which in its historical roots might be traced back to the Greek philosopher, Plato, and his Republic, resulted in some contradictory socio-political and economic philosophies, and has influenced the development of different types of urban settlement throughout history. In the second half of the twentieth century, with growing awareness of environmental problems and ecological crises, the search has been transformed to address the question: what is the sustainable city? There are many uncertainties in the identification of alternative urban forms. This paper examines the two predominant and contradictory theories that are put forward as the grounds for achieving sustainable city forms: the Compact City and Urban dispersal ideas. A study of four different urban forms in the U. K. which were selected and examined systematically in terms of their densities and land uses, is described. The results are mostly supportive of the compact city, particularly in terms of energy efficiency and accessibility to the city facilities.