In Euclidean geometry, the ratio of the circumference of a circle to its diameter is an irrational number, 3.14159 and so on. But if you change to non-Euclidean geometries, you get other values for that ratio. I would like to know if there are any geometries where the ratio is a rational number.
I found this similar question, but that question asked if pi had other values in non-Euclidean geometry... the answers given, although correct technically, all got caught up on the fact that pi is pi regardless of geometry in modern mathematics, so they ended up missing the real question being asked. Thus I am re-asking the question specifically about the circumference-diameter ratio.