Online multi-participant virtual-world systems have attracted significant interest from the Internet community but are hindered by their inability to efficiently support interactivity for a large number of participants. Current solutions divide a large virtual-world into a few mutually exclusive zones, with each zone controlled by a different server, and/or limit the number of participants per server or per virtual-world. Peer-to-Peer (P2P) systems are known to provide excellent scalability in a networked environment (one peer is introduced to the system by each participant), however current P2P applications can only provide file sharing and other forms of relatively simple data communications. In this paper, we present a generic 3D virtual-world application that runs on a P2P network with no central administration or server. Two issues are addressed by this paper to enable such a spatial application on a P2P network. First, we demonstrate how to index and query a 3D space on a dynami...