This study explores the representation of national identity in Iran's architectural heritage from the first to fifth Hijri centuries, addressing how pre-Islamic traditions—particularly Sasanian elements—were reinterpreted within an Islamic framework, contributing to subsequent discourses of Iranian national identity. Its aim is to uncover the mechanisms of continuity and transformation in architectural symbols, motifs, and spatial logic during the transition from the Sasanian to the Islamic era, when this heritage became a foundational source for national narratives of the "Iranian past." Theoretically, the research draws on the ethno-symbolist approach in nationalism studies, especially Anthony D. Smith's works and theorists of historical nation origins and ethnic symbols. In this framework, architecture serves not merely as forms and techniques but as a symbolic medium that rearranges pre-Islamic visual signs within an Islamic context, thereby establishing narratives of Iranian continuity, authenticity, and cultural distinction.Methodologically, it integrates historical-discourse analysis with comparative visual approaches, intertwining historical, artistic, and analytical texts with systematic readings of visual evidence-stucco work, carvings, brick patterns, and vegetal/geometric motifs. Monuments such as the Tarikhaneh Mosque of Damghan, Fahraj and Shushtar Jameh Mosques, Ismail Samani Mausoleum, Isfahan Jameh Mosque, Gonbad-e Qabus, and Khargan Towers are comparatively examined, with textual arguments supported by images, reconstruction drawings, and geometric analysis to reveal tangible links between spatial organization and identity concepts. Findings indicate that the continuity of Sasanian vegetal/geometric motifs, spatial organization, and structural logic in early Islamic architecture transcends mere formal persistence, involving symbolic reinterpretation. The imperial past is integrated and re-signified within the emerging Islamic paradigm. Across the first five centuries, this process generates a symbolic architectural system of spaces and signs that lays the aesthetic and semantic foundations for later patterns, positioning this heritage as the core of early narratives distinguishing and perpetuating "Iran" from other nations.