One way to add depth to your art is to overlap things. I like how this project created lots of very full compositions today, no scrawny buildings with too much sky. That happened because students were instructed to work in layers. First they made a row of buildings across the bottom front, or foreground. Then individual or rows of buildings could be added in the middle, and then background. No sky, no sidewalks, no curtains, no cars, just lots of buildings and windows. When complete, they used watercolor trays to paint everything as they desired. Another plus? Even though the paper was relatively small, (6? x 9? to fit in our art journals) most students used all of the 45 minutes to complete their picture.