The Urban Unseen project examines interstitial spaces found between Victorian-era (1850-1890) residential buildings in the central part of San Francisco. Void spaces, variously referred to as “recesses,” “notchbacks,” “spacing,” “light-wells,” “side-yards,” or as I call them—“slots, ” were primarily introduced to bring sunlight and air into the inner rooms of the long and narrow Victorians. Numerous spaces were lost in the urban transformations of the twentieth century, as Victorians were destroyed during urban renewal, yet many survive in the city’s historic neighborhoods, adapted from their original use as light-wells, to now function as gardens, side-yards, garages, and entrances. Despite their apparent visibility, use, and distinct aesthetic, slots have inadvertently resided in what Walter Benjamin calls our “optical unconscious”—spaces we see but never register, thus remaining mostly overlooked, undocumented and undiscussed.