Karel uses light, glass, and geometric forms to make illusionistic sculptures that challenge the viewer’s perceptions of space and dimension. He especially likes to work outdoors, where his constructions can interact with the environment, absorbing color and light. The interior of Blue Cone’s square base has a hollow space that mirrors the shape of the solid cone that sits on top of it. When light penetrates the sculpture, the hollow interior cone looks like two cones. The form that is seen is the result of refraction; the double cone does not actually exist.