Qing Lu, Hao Li
Digital twin (DT) technologies are increasingly promoted for smart-city governance, yet many deployments remain fragmented and fail to support integrated lifecycle operations across planning, construction, and long-term management. This study proposes a digital-twin–driven urban lifecycle paradigm and examines its city-scale implementation through a structured case study of the Singapore–Nanjing Eco Hi-Tech Island. The study synthesizes a five-layer technical architecture encompassing sensing, data platforms, analytical modeling, service integration, and application scenarios, and organizes eight digital twin application domains spanning governance, community, education, transportation, industrial parks, ecology, security, and tourism. To demonstrate the scale and operational trajectory of the implementation, the paper reports phased quantitative deployment targets and lifecycle indicators (2020–2030), including environmental monitoring coverage, digital infrastructure penetration, public service integration, and governance digitalization. By linking scenario-based demand–supply data matching with lifecycle-oriented indicators, the case illustrates how digital twins can function as an enabling infrastructure for coordinated urban governance beyond isolated pilot projects. The findings offer transferable design and implementation insights for cities seeking to operationalize digital twins at the city scale.