Koh uses two-dimensional photography to create holographic, three-dimensional constructions. His photo sculpture has a transparent surface that reflects the images of the world, and yet reveals the emptiness of its interior space. The overlapping planes create an illusion of indefinable depth and varying imagery, depending on the viewing angle. Building-25 has a structure that uses photographic images of a building's interior on its surfaces, blurring the perceptual boundary between the interior and the exterior. The photographs used for its façade are of the interior of the Pantheon and were taken in Paris in 2006.