I teach a class on Fridays called "MART" to a group of Grade 4 - 6 students. Another teacher and I team teach the class- it's essentially Math inspired art projects.
There's great instructions on the website and we more or less followed them.
Pi (π) is the ratio of a circle’s circumference to its diameter. Pi is a constant number, meaning that for all circles of any size, Pi will be the same. The number pi is extremely useful when solving geometry problems involving circles.
The kids started off by painting their background on a sheet of heavy 9x12" white paper. They could use any media the wanted- most chose to use liquid watercolours.
While the backgrounds were drying, they created their city skyline. I gave them each a printout of the Pi number. Using regular school graph paper, they started with the first number (3) and coloured in (using markers) the first three squares vertically on the graph paper. Then they went along the graph paper horizontally, colouring in the next number in Pi. They only got to use about 19 numbers, more or less, before they ran out of paper, but some of the keeners taped graph paper together to allow for a longer number!!
Once the skyline is coloured in, carefully cut it out and glue stick it to the painted background paper.
Grade 4,5 finished artwork :)