This paper describes the conceptual, aesthetic, hardware, and software design of Flow, a photo/media-based permanent public interactive artwork in Vancouver, Canada. The work is located at street level in a new local community centre at one of the city's oldest intersections. In addition to the community centre location, it has a related interactive web component. It involves the animation and projection of continually recombining photographic images onto a large, interactive 4x4 array of electronically controlled switch glass windows. Over the course of the day and night, these photographic tableaux appear on the glass in combinations that depend upon image-to-image relationships, time of day, season and weather. In addition, lighting elements including water effect gobos are integrated at selected times of day. Images disappear when viewers inside the building come within close proximity to the work: the interactive windows respond to movement by changing from translucent to clear. In the daytime, when the projected image is off at the site, the work continues on the project's website, offering the visitor an interaction with the work. The work aims to provide an experience of the flux of people, animals, landscape and urban environment over time. It addresses the way landscape has transformed in response to colonialism, capital and local pressures, where change is rapid and histories are lost and rewritten.