  Many large cities are found at locations with certain first nature
advantages. Yet, those exogenous locational features may not be the most potent
forces governing the spatial pattern of cities. In particular, population size,
spacing and industrial composition of cities exhibit simple, persistent and
monotonic relationships. Theories of economic agglomeration suggest that this
regularity is a consequence of interactions between endogenous agglomeration
and dispersion forces. This paper reviews the extant formal models that explain
the spatial pattern together with the size distribution of cities, and
discusses the remaining research questions to be answered in this literature.
To obtain results about explicit spatial patterns of cities, a model needs to
depart from the most popular two-region and systems-of-cities frameworks in
urban and regional economics in which there is no variation in interregional
distance. This is one of the major reasons that only few formal models have
been proposed in this literature. To draw implications as much as possible from
the extant theories, this review involves extensive discussions on the behavior
of the many-region extension of these models. The mechanisms that link the
spatial pattern of cities and the diversity in city sizes are also discussed in
detail.
