I did this simple art project with my nephew and my two littles several months back. I can't take credit for this idea though--I got it from Let's Explore, one of my favorite blogs to visit for craft ideas.
This was super easy and is pretty self explanatory, but here are the directions anyway:
--large piece of watercolor paper
--yellow and black construction paper
--scissors, glue and watercolor paints
1. Have the child use sunset (warm) hues to paint horizontal lines across the watercolor paper. None of mine followed the warm hues very well, but it was still really pretty in the end. :)
2. Depending on the age of the child, cut out or let them cut out different sized rectangles from the black paper for buildings and skyscrapers. Cut out squares for windows out of the yellow.
3. Once the watercolor is dry, use a glue stick to glue the buildings and windows on.
Result: One beautiful piece of artwork for your living room wall. :)