The rapid technological evolution,which is characterizing all the disciplines involved within the wide concept of smart cities,is becoming a key factor to trigger true user-driven innovation.However to fully develop the Smart City concept to a wide geographical target,it is required an infrastructure that allows the integration of heterogeneous geographical information and sensor networks into a common technological ground.In this context 3D city models will play an increasingly important role in our daily lives and become an essential part of the modern city information infrastructure (Spatial Data Infrastructure).The work presented in this paper describes an innovative Services Oriented Architecture software platform aimed at providing smartcities services on top of 3D urban models.3D city models are the basis of many applications and can became the platform for integrating city information within the Smart-Cites context.In particular the paper will investigate how the efficient visualisation of 3D city models using different levels of detail (LODs) is one of the pivotal technological challenge to support Smart-Cities applications.The goal is to provide to the final user realistic and abstract 3D representations of the urban environment and the possibility to interact with a massive amounts of semantic information contained into the geospatial 3D city model.The proposed solution,using OCG standards and a custom service to provide 3D city models,lets the users to consume the services and interact with the 3D model via Web in a more effective way.