The subject of the present work is the study of the relationship between the city’s shape and its natural context. The ‘design’ of cities over a territory doesn’t happen independently of its natural context. The surface of the land has already its own form which determines the pattern of many cities. The climate characteristics also suggest different sites and forms of occupation. As a result of these constrains, man has made beautiful and sustainable urban landscapes over the time, especially those non-planned cities, called organic, generated, vernacular, spontaneous or geomorphic. Many of them, like the Mediterranean cities, have so strongly accepted the natural features, that it is possible to identify urban patterns according to its natural environment. The study of the urban form is associated to the idea of rational planning and the production of a model. The territory, as the base for our activities, has been seen many times as an element which generates irregularity to the urban form. The objective of the proposed paper is to show the relationship between the structural quality of the Portuguese traditional cities and its natural context. Starting from this point we try to explain the genesis and growth of urban forms, especially those called organic or geomorphic.

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