I love all things that are quirky in geometry (e.g. the Reuleaux triangle) so this one naturally impresses me. It’s called a Gömböc, and no matter which way you put it down, it will right itself - without having a weight at the bottom. It’s the only shape that can do this.
Legitimus Maximus will probably enjoy this the most, because apart from being a math lesson, Turtles with short legs have naturally evolved to this shape to make it easier to right themselves when flipped over.
