A 3D city model is a digital representation of a city or an urban fabric, using data derived from multiple sources. It encompasses a large number of spatial objects that can gather various levels of detail, scales and can be of different classes, data models or structures. It is an important tool used in various fields such as urban planning and management, facility location, or car-navigation systems, as well as for research and 3D visual representation of the urban environment as textured images or fly-through. Because such models can be integration axis of various knowledge related to several urban or environmental issues, they are increasingly used for an intended wide range of applications. Since its kick-off meeting in spring 2008, the European Cost Action TU0801 (Semantic enrichment of 3D city models for sustainable urban development) aims to delineate and organize several issues related to this complex and composite research object. As the final event of this action, the “3u3d2012: Usage, Usability, and Utility of 3D City models” conference was organized to address the three issues that actually gave their names to the conference. This event was held in the Graduate school of architecture of Nantes (France) from Oct. 29 to Oct. 31, 2012.