Intro: It's Pi. But It's Cake. But It's Pi. BUT IT'S CAKE!
This is actually a cake that I made using a 9x13" pan. I baked one layer, set that aside, baked another layer, and placed one on top of the other, with frosting and chocolate chips between. Then I cut the image of Pi out of the layered cake using a long knife, frosted the sides in chocolate frosting and the top in buttercream. I took it to my school's Pi day celebration,and it was the centerpiece of the Math department table. No one wanted to cut it. It ended up being about 5 inches tall, and 9x13 as viewed from above.