I want to know how impassable mountains make a world feel larger? They dont, if anything they make the world seem smaller. look at NV invisible walls for the proof. With that said, I dont care if its a little smaller than Ob. I just dont see how impassable areas make a world feel larger, when they dont.
It is probably wrong of me to describe the mountains as "impassible." In truth, you can pass over the mountains, just not by a direct rout; so instead of just looking at your compass and going in the direction it tells you to go, you have to devise an indirect more intricate rout with many turns to arrive at your destination—walking zig-zag from point A to will B will take longer than walking directly in a straight line from point A to point B. You cold also think of it like this: if the sense of a space's size is derived from the time it takes to traverse that space, the protraction of time to traverse the space will make the space feel larger despite actually being the same size.
Another important concept to keep in mind is surface area versus topographic area. Think of looking at a paper pyramid on a table from above. Then think of unfolding all its sides and facing them separately flat on the table. From above, the unfolded pyramid looks to cover more area than it did when folded, but its surface area has not changed. The mountains will behave much the same way, not only lengthening the time it takes to traverse the land, but also giving the developers more surface area to pack content.