Map of the Twin Kingdoms of Aran and Ilan - Handdrawn

[Pixie]

I'm all for revising mountains as to make them "tectonically" realistical, everytime. But that's me, my 2 cents say you are in the right track.

But could I point a fact about realistical impenetrable ridges? They normally have some form of plateau on one of the sides. Himalayas are pretty much impenetrable, but there's the Tibetan plateau; Andes are the most straight up ridge from the ocean you can think of, and there's the andean plateau, from California inwards (say San Francisco-Reno) it's pretty much up, but then it's always in altitude to Utah, there's a ridge between Iran's mainland (which is a plateau) and the Persian Gulf...

So, consider that... That big lake, for example, about half way up from the center, could be in altitude..

Also, (and I know I may not be helping)... Older mountain ranges (no longer active) would already have had glacier erosion at some point. This creates easily crossable valleys.. see the Alps, or the Scandinavian ridge, for an example. Plateaus, on the other hand, don't really have glaciers, at most they'll end up with spread out lakes/depressions of various sizes.

A desert/frozen plateau could be just as impenetrable for an army on the march as a couple of peaks lined up. You can still make it fit in your imagined setting.