CityGaussian is a research project for high-quality large-scale 3D scene reconstruction and rendering using Gaussian Splatting, a neural rendering technique. The system takes multi-view images and reconstructs scenes as 3D Gaussians that can be rendered from novel viewpoints in real time. It includes CityGaussian (ECCV 2024) for real-time large-scale rendering and CityGaussianV2 (ICLR 2025) for more efficient and geometrically accurate reconstruction with level-of-detail support.