Urbanism in Islamic Mediterranean is deeply linked to courtyard houses characteristics and structure. Consequently, courtyards represent the most important element of the Syrian historical urban landscape determining the dimensional relationships between open spaces and built surface (which depends on the need to effect the best microclimate); the aggregative logics of rooms around the courtyard; the orientation and use of 'specialized' rooms and structures to control the microclimate inside the house; and the steady aggregative logics in elements constituting bayts (houses or rooms) and ksars (palaces). The aim of this paper is to describe the invariant characteristics of Syrian historical urban landscapes, focusing on the structure of courtyards and inner gardens. To this end, the cases of Aleppo, Damascus, and Hama will be analyzed, with the purpose to highlight: the aggregative logic shaping the houses around the courtyard; the relationship between architectural features of the house and garden structure; the relationship between inner gardens and architecture; and the relationship between traditional housing (even palaces) and courtyards. These are the invariants that must be considered and / or preserved in a project of urban landscape recovery or design.