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-40 is an imaginary building made with photographic images taken in Grand Central Station in New York. The images of the inside of the station were captured over four intervals in 2008 and collaged to form a structure where different temporal scenes coexist.