Do they know that their world is a sphere?

I was just wondering if the people in Warcraft know that their planet is a sphere and NOT a rectangle or square or some other unusual 2-D shape. I'm asking, because if they don't know, I can't make references to it in OtbL. Does anyone know if this is confirmed?

EDIT: I know that there is evidence to it, like the Arcane Sanctum. However, I don't think this was ever confirmed.

Well, the elves should know it (both night and blood) which consequently means that everybody now does, in WOW, all the races have interaction with each other even across the horde-alliance front.

Good enough for me. Now I have a hilarious conversation regarding- *spoilers*.

Wait, how do we know that their world IS a sphere?

edit: Besides the fact that their map makes sense if it was wrapped around a sphere.

Look at the world of warcraft logo.