This paper presents a structural evaluation of the unreinforced masonry ribbed barrel vaults (UMRBV) in Bahri Mamluk religious buildings in Historic Cairo. The research evaluates the structural functions of ribs in UMRBV by comparing its structural stability under various expected loading conditions with non-ribbed vaults. The aforementioned structural analysis is applied to the vault of the main iwan of Sultan Hassan Madrasa, the largest iwan in Historic Cairo. This research starts with a brief historical and architectural study. I conducted a building material investigation of the iwan using XRD, PLM and SEM-EDX. A comprehensive structural analysis employing a finite element method is conducted on the iwan using well-established software (SAP2000, Release 20). The study also incorporated a comparative analysis of iwan models with and without ribs, employing both 3D-shell and solid elements within the chosen software. The results demonstrate a substantial improvement in the structural performance of ribbed models compared to their non-ribbed counterparts. This enhancement is evident in a reduction of up to 46.5% in deflections and up to 44.2% in stresses, observed under static and dynamic loading conditions. Based on the results obtained, a concise recommendation for strengthening methods is proposed.