Abstract: This paper describes a prototype application named that implements a Large Scale Virtual Environment (LSVE), combining a 3D world, textual messages, multimedia communications and High Definition video. When developing , our primary goal was to create a platform suitable for easily experimenting multimedia transmission, with a large number of participants, and on heterogeneous IP networks, e.g. combining a very powerful backbone such as VTHD, together with wired LANs, as well as WLANs in the IEEE 802.11 family. In particular, this platform is very useful for evaluating the scalability of transmission protocols and the support of differentiated services for multimedia applications. uses the communication architecture. In this approach, agents perform a real-time mapping of the geographic area into spatial areas whose sizes depend on the density and location of participants; each of these cells is associated with a multicast group. In this way, each participant can focus on his area of interest, and receive only the relevant traffic.