Originally Posted by Sabretooth
I don't know what you're talking about.
It's quite simple. Look at this map I've roughly compiled from PipBoy screenshots:
Notice anything? As I said in my previous post, at least a third of the map is empty and inaccessible (unless you use noclip). And looking at it again, it's actually more like half the actual physical landscape. So either they are planning on using that space for DLC, or they just made it that big to give the illusion of something comparable in size to FO3.