I think there used to be one by New Bark, otherwise I'm not really sure how you'd get across... And I'm not sure, we might be connected to something else beyond the mountains? I haven't traveled very far yet.

_{[Maybe people can fly across it--but some of these Pokemon that can use Fly are awfully tiny...]}

I have two fire, a water, two electric, flying... and I think a dragon? But I've read a book that has a lot more, like ghost-types and grass. If you travel on the routes at night, I think you can bump into a couple of the former.