Inspired by the UK National Infrastructure Commission’s ambition of building a “digital twin” for the national infrastructure, this paper reviews some of the latest progress on digital twin development in the UK, particularly the recently published report “The Gemini Principles” by the Centre for Digital Built Britain. The paper further puts forwards six propositions on the city-level digital twin agenda, which stem from an ongoing research project on smart cities at the Cambridge Centre for Smart Infrastructure and Construction. It is argued that the development of a digital twin is progressive, where the digital twin as a technical apparatus and the social system that develops, operates and uses the digital twin must co-evolve together. On the one hand, our existing knowledge about cities and infrastructure would define how well we could build and evaluate the digital twin; on the other hand, thanks to artificial intelligence, the digital twin could potentially produce new knowledge that complements ours. In the context of developing smart cities, the paper points out that the digital twin is not a context-free technology that can be simply purchased and installed onto existing governance systems. To develop a purposeful digital twin application, the insights and changes from the governance perspective are essential. The paper also introduces the research plan for developing a digital twin pilot for the Cambridge sub-region, which serves as a case study to test the proposed propositions.