OpenCity3D: What do Vision-Language Models know about Urban Environments?

The rise of 2D vision-language models (VLMs) has en-abled new possibilities for language-driven 3D scene understanding tasks. Existing works focus on indoor scenes, or autonomous driving scenarios and typically validate against a pre-defined set of semantic object classes. In this work, we analyze the capabilities of vision-language models for large-scale urban 3D scene understanding, and propose new applications of VLMs that directly operate on aerial 3D reconstructions of cities. In particular, we address higher-level 3D scene understanding tasks such as population den-sity, building age, property prices, crime rate, and noise pollution. Our analysis reveals surprising zero-shot and few-shot performance of VLMs in urban environments.