Rendering large city models with high polygon count and a vast amount of textures at interactive frame rates is a rather difficult to impossible task as it highly depends on the client hardware, which is often insufficient, even if out-of-core rendering techniques and level of detail approaches are used. Rendering complex 3D city models on mobile devices is even more challenging. An approach of rendering and caching very large city models in the cloud using ray-tracing based image provisioning is shown in this talk, which allows rendering large scenes efficiently, including on mobile devices. With this approach, it is possible to render 3D city models with nearly unlimited number of polygons and textures. Several Python scripts for rendering 3D city models in the web browser are shown.