I think everyone is looking at things differently here. I believe the original question was: Is Achaea shaped like a ball, or like a dinner place, or something like that.
Now, the evidence other lands exist beyond Sapience is by no means proof that Achaea is shaped like a ball.
And mountains and such are by no means proof that it is not flat, or more accurately, spherical. It can still be bumpy and not be spherical.
There are other lands out there, I myself have travelled extensively when day to day business makes my brain hurt, but the fact that you can sail to other lands, does not prove that the world is spherical by any means.
Now, if you can sail to these other lands, go around them and continue in a strait line and find Sapience, there is your proof.
The fact remains that the sun rises and sets at the same time in Shallam as it does in Ashtan and that the stars look the same wherever you stand.
If you look to the horizon and see what seems to be a curve, well, this is merely a well known trick of light and vision. Everyone knows if you view something from a distance, it looks smaller.
Therefore, standing on a beach where the sea is right before you, it would seem to get lower as it got further away. As any artist would tell you, this is called perspective.
The idea however, that you would fall off the edge of the world is rediculous. How would the Gods in their divine wisdom create a world in which all the water in the sea would flow right off the edge? The sea would be able to hold no water.
You get to the edge and it stops, thats it. You can go no further and that is all.
No, the world is not flat, it is quite bumpy, but the evidence is overwelming that the world is NOT shaped like a sphere, a ball, a pear, or a carrot. Untill someone can set sail from Shallam heading South and land in Ashtan, I shall hold this belief.
For it is the only one set in any form of logic.

Penned by my hand on the 6th of Valnuary, in the year 245 AF.