(Not the actual picture my co-worker took - that comes later.)
This was so fascinating to me that I spent the next hour reading about the geocentric model of the universe, trying to understand how this illustration came to be. Apparently, it's based on a Biblical passage (Revelations) that talks about angels on the "four corners of the Earth":
As you can see, this Earth model has the northern hemisphere as a convex shape inside a concave one (the southern hemisphere). I assume that the concave shape prevents the oceans from leaking into space, but wouldn't that also mean that Africa and Australia are constantly under water?
I'm sad to report that I still don't have an explanation for the shape and placement of the Earth in this illustration.
My favorite part was this "debunking" of the theory that the Earth moves through space:
I highly encourage you to visit this website, which has taken the time to review the current International Flat Earth Society's website for humorous rationale and a marvelous FAQ. (No sense in giving the IFE any ad revenue.)