Rapid urbanization and the growing complexity of multi-level buildings have exposed the limitations of Iran’s current two-dimensional cadastral system in accurately representing property boundaries and legal rights. To address these challenges, this research develops a prototype framework for implementing a three-dimensional (3D) cadastre based on the OpenBIM1 approach and the IFC2 standard. The proposed methodology transforms existing 2D cadastral data into 3D representations by integrating geometric, semantic, and legal information within a unified BIM environment. Unlike previous studies that relied on proprietary software or partial data integration, this research exclusively employs free and open-source tools to ensure interoperability, transparency, and vendor independence. The prototype was tested on a real apartment building in Tehran, demonstrating the feasibility of modeling both physical and legal spaces— such as ownership units, shared zones, and easements—through standardized IFC object classes and property sets. The resulting 3D model complies with international standards and aligns with the current land administration workflows in Iran. The findings confirm that OpenBIM-based modeling provides a practical foundation for establishing 3D cadastre in Iran, improving property registration accuracy, supporting advanced spatial analysis, and enhancing urban management. The study also emphasizes the importance of incorporating elevation data in cadastral surveys and developing a legal and institutional framework for the adoption of 3D cadastral systems nationwide.