A nifty mathematical object, sliced on the diagonal to expose the internal structure and permit printing without rafts, support, or horizontal spans. Added 1- and 2-level sponges as well. When printed smaller, I think the 2-level sponge comes out very nicely. You can create your own variants using NetFabb Basic as follows: Create a Menger Sponge (it's a primitive) Rotate Z axis by 45 degrees, then Y axis by 54.73560912600694 degrees. Slice off a corner by cutting along the Z plane (make fine adjustments by 0.1mm in the slicing dialog to get it just right) Remove the bottom segment, creating the flat base. Export as STL, and resize in your slicer. For small prints, a 1- or 2-level sponge is probably best