A league is one of those vague terms from the old days when europeans measured distance in terms of how far they could walk or ride in a given amount of time. I believe a league has no set value, but it's safe to say it's around three and half miles. That would make the Ermine what, about 250 x 150 miles? That's a pretty decent sized forest, but relatively small for two tribe-races to be sharing.
Re: The Stair, I don't have GURPS. Does it simply say the Stair is 125 miles of travelling? Because it could mean that in terms of crossing them, not their longitudinal width. Let me know.
-David
