Urban planning in the era of large language models

City plans are the product of integrating human creativity with emerging technologies, which continuously evolve and reshape urban morphology and environments. Here we argue that large language models hold large untapped potential in addressing the growing complexities of urban planning and enabling a more holistic, innovative and responsive approach to city design. By harnessing their advanced generation and simulation capabilities, large language models can contribute as an intelligent assistant for human planners in synthesizing conceptual ideas, generating urban designs and evaluating the outcomes of planning efforts. Large language models remain largely unexplored is the design of cities. In this Perspective, the authors discuss the potential opportunities brought by these models in assisting urban planning.