Returning to the idea of 2D mixing with 3D, JJK Airbrush has created some incredible illusions with nothing but pencil, paper and a rubber.
The attention to how light works and reacts is perhaps the key here. The accuracy of the shadows forces your eyes to believe that the pencils really are resting on the rocks. I love the idea of using illusions somehow, creating the idea of shapes and forms being present through pretend shadows for example. This could be a fascinating addition to any piece of architecture.