Historic urban squares are not only significant public spaces where commercial, social, cultural, and political activities take place, but they also rank among the fundamental elements that reflect urban identity and cultural heritage. With their architectural structures, historic fabric, and traditional features, these squares add aesthetic and social value to urban life by bridging the past and the present. This study examines Naqsh-e Jahan Square in Iran and Sultanahmet Square in Turkey using a comparative spatial analysis method. The aim of this research is to investigate how spatial structure, architectural framing, landscape integration, and urban furniture elements contribute to the identity and functionality of historic urban squares. Furthermore, the study aims to quantitatively assess spatial openness and permeability and evaluate their influence on accessibility, connectivity, and the overall functionality of public space. The research methodology is based on a mixed-methods approach that integrates qualitative observations, visual documentation, and historical mapping with quantitative spatial indicators, including the Spatial Openness Index (SOI), Permeability Ratio (PR), and Edge-Defined Score (EDS). The findings indicate that the physical attractiveness and functional success of a city square are directly related to a high-quality architectural environment, harmonious spatial design, and appropriate urban infrastructure elements. Furthermore, cultural diversity, the facilitation of social and cultural activities, the integration of historical fabric with contemporary functions, appropriate lighting, and vibrant commercial activities emerge as key factors in the social and cultural sustainability of historic squares. The study contributes to the literature by establishing a quantitative framework for assessing urban squares and identifying the factors that support the long-term continuity and preservation of historic public spaces.