Abstract
Based on threshold analysis theory, spatial limiting factors such as mountains, rivers, and roads not only affect the way in which cities spread out, but also play a vital role in shaping the flattened forms of their central districts. This study, based on field investigations of 21 central districts in 13 Asian megacities, seeks out limiting factors that determine the boundaries of urban central districts by quantifying the spatial boundary and distance of the limiting factors. The results suggest a strong correlation between the spatial limiting factors and the urban central district′s form. The limiting elements constrain the size of buildings and population density based on floor area ratio, building density, and development boundaries. Reduction in population and the inconvenience of traffic have decreased urban vitality, leading to delays in the extension of cites′ central districts. It is necessary to fully consider the role of the city′s internal limiting elements in order to reasonably plan the construction of an urban central district.
