Here's a proof of the inequality of the arithmetic and geometric means in the form $$\frac{x\_1^n}{n} + \cdots + \frac{x\_n^n}{n} \geq x\_1\cdots x\_n.$$
Proof for $n=3$:
The "figure" for general $n$ is similar, with $n$ right pyramids, one with an $(n-1)$-cube of side length $x\_k$ as its base and height $x\_k$ for each $k=1,\ldots,n$.
(I made this in Inkscape, a wonderful free-software vector drawing application. For the inequality and associated labels, I used the textext extension.)
