I'm in the process of refining my world that I've been writing in for a long while now (my brief foray into a high fantasy world was short, I'm back to the world I never should have left, and I am half way through writing the first draft of a novel), as I've come to a point in my writing where more details are needed.

Geographically, for a whole continent that's supposed to be rather large (if you combined all the continents together, it would be the largest part of them, and in the center), how many rivers/mountains vs. flat grasslands vs. highlands vs. deserts and the like would seem realistic, or is that all something that's up to the author? As it is, I'm going through each "section" for the map and making a list of what should be there, and I don't want to over-burden an area with too much stuff or have it have too little >.>