Various countries of the world endeavor to achieve a new paradigm of sustainability by preserving their heritage and history and avoid the risk of old process preservation. Therefore, this article adopts several concepts for investigating heritage areas and then builds a model based on spatial analysis using GIS. So, the main problem this article addresses is that planning does not rely on appropriate mechanisms for preserving the heritage area of Al-Nasiriyah in Dhi-Qar Governorate, Iraq, which has resulted in erosion and destruction of that area. Consequently, the article aims to determine the optimal process for the rehabilitation to the heritage city center, using spatial analysis mechanisms and to achieve urban sustainability. To do this, the article first discusses various countries' experiences in the field of heritage conservation to understand successful principles for implementing the new sustainable paradigm. Subsequently, the Analytical Hierarchy Process (AHP) is used to calibrate and assign weights to the analysis mechanism. This process is based on the most prominent elements that depend on land uses and necessary services in the spatial analysis. After analyzing eight indicators, a consistency ratio of 0.47 was obtained, which is the acceptable excitation range in AHP standards. Finally, the study built a model in GIS to determine the most suitable area for the development of any city with the same condition. Therefore, the spatial analysis and model process identified Zones 2 and 3 as the most suitable for development, with Zone 4 being the optimal choice according to the MCDM analysis to be selected as the first area for development. Thus, this can limit the process of erosion of the urban heritage fabric due to the encroachment of commercial use and the rise in the value of achieving cultural sustainability.