Empire State building
When I'm in my darkest moods, I can convince myself we're all destined to be living in cardboard cities someday soon.
Now that's I've seen how they could look (these were made by middle schoolers at Ittybit's school), I'm not as worried.
Materials: Boxes, masking tape, pencil and Sharpie. (I imagine a yardstick was also among the tools.)