A Menger sponge
is a 3D fractal that starts with a cube. In each iteration the surface of each cube is divided into 9 sections and the middle section is pushed out.
In the next iteration, you look at the smaller subcubes of the original cube and repeat the same process.
in the picture below you can see the same process. With this gingerbread fractal we'll be making a level 2 Menger sponge and using decoration to make it look like a level 3.
Don't worry if that doesn't make sense, we'll move out of math geek territory now.