The camera obscura has always had a strong relationship with its environment. The relationship, however, is one-directional: the camera takes in the surrounding through a small hole and projects the image into an enclosed space. For the Breda photofestival, we proposed a camera obscura that creates a dialogue with the city. Using mirrors and photosensitive emulsion the camera obscura would project an image of the city onto the ground. During the festival the mobile camera obscura moves through the city, leaving a trail of images that form a growing open air exhibition: an imprint of the collective imagination.