Research on the historical spatial characteristics and conservation strategies of colonial cities in Asia and Africa: a case study of 21 typical cities

Colonial cities in Asia and Africa, developed under the dual influence of native and sovereign cultures during the colonial era, exhibit unique urban morphological characteristics and reflect the planning ideologies of diverse cultures. Thus, the morphological study of colonial cities in Asia and Africa is crucial for understanding and identifying the historical and cultural value of these cities, which in turn enables the formulation of precise conservation strategies. In light of this, the study develops an urban morphological analysis methodology comprising "Colonial Background Analysis—Morphological Characteristics Analysis—Driving Factor Extraction" based on the Conzenian Approach, which is used to examine the morphology of 21 typical colonial cities in Asia and Africa across various colonial periods. As a result, "Dual-City" emerges as the core spatial characteristic of colonial cities in Asia and Africa, reflecting the morphological differences in road layouts, urban fabric, and urban cores between native and European zones. Additionally, as native settlement sizes, social structures, and cultural identities differ between cities, three major spatial patterns of the "Dual-City" model can be identified: separated, mediated, and integrated spatial patterns, resulting from the varied planning approaches applied by colonizers. Furthermore, suggestions for the conservation of colonial heritage are proposed based on the driving factors analysis from the morphological study.