The document discusses 3D city models (3DCM), which are digital representations of urban areas like cities and buildings. 3DCM have various applications in fields like urban planning and engineering. The document reviews literature on 3DCM projects, including cases modeling the cities of Hamburg, Germany and Fez, Morocco. It also describes two case studies modeling the cities of Vadaj, India and parts of Mumbai, India using software like ArcGIS. The 3DCM allow for better visualization and analysis of spatial properties, land use, and infrastructure to inform decision making.