I think I was around seven years old when I first realized that if only there were spiral escalators, the world would be a better place. I am sure it's a common realization.

So I finally set out to design one. The accompanying applet shows just the basic principle.

What it doesn't show: (a) the helical groove in the central shaft that contains the drive belt and motors, and (b) the outside railing that guides the leading and trailing edges of each moving/rotating stair step.

- Ken Perlin