CityGML is a recent standard developed to describe, store and exchange virtual city models. Numerous software programmes have been proposed to construct, edit, modify and visualize city models, but visualisation in a web browser is still challenging. In this paper we propose a framework based on standards for visualising a large amount of 3D city data. CityGML files are processed automatically to provide a city model composed of geometries, textures and semantics. Exchanges follow the pending Open Geospatial standard named 3D portrayal. In this paper, we also demonstrate that a solution where semantics and geometries are exchanged together is possible. An effort has been made to show that an approach based on progressive textures may also be possible.