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. Stairway-3 provides a surreal building with an empty building inside and a stairway outside. While the outer building has a sky photograph superimposed on it, the inner building has a wave image. These images are overlapping each other, visually complicating the piece's layered space.