We describe a system for supporting mirror worlds – 3D virtual models of physical spaces that reflect the structure and activities of those spaces to help support context awareness and tasks such as planning and recollection of events. Through views on web pages, portable devices, or on ‘magic window’ displays located in the physical space, remote people may ‘look in’ to the space, while people within the space are provided information not apparent through unaided perception. For example, by looking at a mirror display, people can learn how long others have been present, or where they have been. People in one part of a building can get a sense of activities in the rest of the building, know who is present in their office, and look in to presentations in other rooms. The system can be used to bridge across sites and help provide different parts of an organization with a shared awareness of each other’s space and activities. We describe deployments of our mirror world system at several locations.