Open-source Risk game - ideas needed

I have been playing around with blender and ogre during the last few weeks and have decided to make an open-source somewhat 3d version of the classic board game RISK. I’ve programmed quite a bit but am new at modeling. Here’s my problem:

Some of my more interesting camera shots call for closeups of terrain. I would really like to make a somewhat realistic world map with mountains, lakes, rivers, etc. I don’t want to get to terribly detailed, but major rivers like the Nile or the Missippi as well as big mountain ranges like the Alps or the Himalayas would be cool to include. A 3d perspective of these features would be very nice.

Can anyone give me ideas of where I would start?

Just create a subdivided plane (not to heavy though, watch the polycount). then model the major form of the land, and use textures for the rest.