From the Mighty Optical Illusions site:
Felice Varini created a piece called Cercle et suite d’eclats, where he encouraged an entire town to help create the illusion of 2D using the 3D buildings of the town. As one person commented about some of his earlier work: "WOW. These. Look. So. Photoshopped. I know they’re not.. but WOW."
Take a look>>