Algeria’s pre-colonial towns of the medieval period still exist in different typologies, ranging from the isolated buildings (forts, castles) and town enclosures to whole urban units (fortified villages, defensives towns). Indeed, the constituent of these fortresses was their defense system, characterized by its large dimension, constituted essentially by the enclosure wall, and architectural features of defensiveness correlated with the outside and the inside of the fortresses. This paper aims to evaluate the relationship between physical landscape, built defensive features and cultural values of the medieval fortified villages in Algeria, two medieval fortified villages in our case “Kalaa of Beni Abbes” in Bejaia and “Kalaa of Beni Rached” in Oran, that we identified as an evolved landscape and interpreted as complex system (both defensive architecture and continuing cultural landscape). This current study consists of quantifying the defensiveness degree of these sites situated within different contexts, in fact, this method ensures to identify the strategy adopted to be protected against different invasions. However, in order to achieve this we calculate a spatial defensiveness index (DI) of these sites. The parameters of our choice are related to the implantation site, the elevation, the visibility and the geometrical shape, which allow us to estimate the defensiveness degree of the defense system of our case studies.