Supposedly square-base pyramids have some interesting properties. They are/were used to harness energy among other things. I can't confirm that it's true, but the stories are pretty interesting. A triangle can be used as a two-dimensional representation of a pyramid. Triangles used in illuminati symbolism are supposed to be pyramids, not triangles. The eye often found within illuminati pyramid/triangle symbolism is the 'eye of providence' and, I believe, represents knowledge/information.