A multiuser, collaborative augmented reality (AR) system employs individual AR devices for viewing real-world anchors, that is, physical models that are recognizable to the camera and image processing module of the AR device. To mitigate ambiguous configurations when used in the collaborative mode, each anchor is registered with a server to ensure that only uniquely recognizable anchors are simultaneously active at a particular location. The system permits collaborative AR to span multiple sites, by associating a portal with an anchor at each site. Using the location of their corresponding AR device as a proxy for their position, AR renditions of the other participating users are provided. This AR system is particularly well suited for games.