The project aims to explore the utilization of digital twins in enhancing smart city applications by focusing on four key functions: object mapping, object relation, data availability, and user interaction. The project will lead to various research topics, contribute innovative solutions, and advance academic engagement in this emerging field. The project will involve developing a comprehensive urban digital twin system architecture, creating an open-source urban digital twin prototype system, and devising optimization algorithms for multiple usage scenarios. The gained insights will support Taiwan's ICT industry in transitioning towards offering comprehensive digital twin-enabled smart city services, thereby promoting industrial advancement. Ultimately, digital twin-enabled smart cities are envisioned to fulfill diverse urban needs, foster inclusive, secure, resilient, and sustainable urban environments aligned with UN Sustainable Development Goal 11: Sustainable Cities and Communities.