Site[edit]
Town siting has varied through history according to natural, technological, economic, and military contexts. Access to water has long been a major factor in city placement and growth, and despite exceptions enabled by the advent of rail transport in the nineteenth century, through the present most of the world's urban population lives near the coast or on a river.[27]
Urban areas as a rule cannot produce their own food and therefore must develop some relationship with a hinterland which sustains them.[28] Only in special cases such as mining towns which play a vital role in long-distance trade, are cities disconnected from the countryside which feeds them.[29] Thus, centrality within a productive region influences siting, as economic forces would in theory favor the creation of market places in optimal mutually reachable locations.[30]
Center[edit]
Main article: City centre
The vast majority of cities have a central area containing buildings with special economic, political, and religious significance. Archaeologists refer to this area by the Greek term temenos or if fortified as a citadel.[31] These spaces historically reflect and amplify the city's centrality and importance to its wider sphere of influence.[30] Today cities have a city center or downtown, sometimes coincident with a central business district.
Public space[edit]
Cities typically have public spaces where anyone can go. These include privately owned spaces open to the public as well as forms of public land such as public domain and the commons. Western philosophy since the time of the Greek agora has considered physical public space as the substrate of the symbolic public sphere.[32][33] Public art adorns (or disfigures) public spaces. Parks and other natural sites within cities provide residents with relief from the hardness and regularity of typical built environments.
Internal structure[edit]
Urban structure generally follows one or more basic patterns: geomorphic, radial, concentric, rectilinear, and curvilinear. Physical environment generally constrains the form in which a city is built. If located on a mountainside, urban structure may rely on terraces and winding roads. It may be adapted to its means of subsistence (e.g. agriculture or fishing). And it may be set up for optimal defense given the surrounding landscape.[34] Beyond these "geomorphic" features, cities can develop internal patterns, due to natural growth or to city planning.
In a radial structure, main roads converge on a central point. This form could evolve from successive growth over a long time, with concentric traces of town walls and citadels marking older city boundaries. In more recent history, such forms were supplemented by ring roads moving traffic around the outskirts of a town. Dutch cities such as Amsterdam and Haarlem are structured as a central square surrounded by concentric canals marking every expansion. In cities such as and also Moscow, this pattern is still clearly visible.
A system of rectilinear city streets and land plots, known as the grid plan, has been used for millennia in Asia, Europe, and the Americas. The Indus Valley Civilisation built Mohenjo-Daro, Harappa and other cities on a grid pattern, using ancient principles described by Kautilya, and aligned with the compass points.[35][19][36][37] The ancient Greek city of Priene exemplifies a grid plan with specialized districts used across the Hellenistic Mediterranean.
Urban areas[edit]
Urban-type settlement extends far beyond the traditional boundaries of the city proper[38] in a form of development sometimes described critically as urban sprawl.[39] Decentralization and dispersal of city functions (commercial, industrial, residential, cultural, political) has transformed the very meaning of the term and has challenged geographers seeking to classify territories according to an urban-rural binary.[17]
Metropolitan areas include suburbs and exurbs organized around the needs of commuters, and sometimes edge cities characterized by a degree of economic and political independence. (In the US these are grouped into metropolitan statistical areas for purposes of demography and marketing.) Some cities are now part of a continuous urban landscape called urban agglomeration, conurbation, or megalopolis (exemplified by the BosWash corridor of the Northeastern United States.)