Techniques for retrieval of multimedia data through visual representations are provided. Such visual representations, preferably in the form of visual activity maps or spatio-temporal activity maps, serve as an efficient and intuitive graphical user interface for multimedia retrieval, particularly when the media streams are derived from multiple sensors observing a physical environment. An architecture for interactive media retrieval is also provided by combining such visual activity maps with domain specific event information. Visual activity maps are derived from the trajectories of motion of objects in the environment. The visual activity map based techniques significantly help users in quickly and effectively discovering interesting portions of the data, and randomly accessing and retrieving the corresponding portions of the media streams.