Visually stunning math concepts which are easy to explain Since I'm not that good at (as I like to call it) 'die-hard-mathematics', I've always liked concepts like the golden ratio or the dragon curve, which are easy to understand and explain but are mathematically beautiful at the same time.
Do you know of any other concepts like these?

The surface obtained by spinning a cube on two diametrically opposite corners:
$\hskip{4.5cm}$
All the surfaces are ruled surfaces. The top and bottom are simply conical caps. The curved part in the middle is part of a hyperboloid of one sheet. It can be obtained by taking a cylinder of radius and height $\sqrt{\frac23}$ times the edge length of the cube and giving one of the ends a $60^{\large\circ}$ twist.
