Nowadays, 3D city models are getting more popular day by day. Achievements in the 3D domain are notable. However, 3D modeling still faces some impediments to be generalized. New solutions such as linking 2D and 3D worlds through 2D/3D data integration should be investigated.

This paper presents an overview of some realizations that have marked out the 3D modeling field and highlights some related questions that are still in the research. It presents and argues the importance of bridging the 2D and 3D worlds as a promising solution to upgrade to integrated 3D solutions in the future. This idea is supported by a case study, to demonstrate how 2D/2.5D data collected from different sources can be integrated and reengineered to match the specifications of a 3D building model compatible with the CityGML standard.