Quote Originally Posted by kidkboom View Post
I think I put the noun in prep. owing to some confusion between prep. and dat. on this one.. Thanks for pointing that out, and especially the verb; I have to remember the clue in -лась / -лся about gender.

So thanks to your help I have two new ways to write this, I'm hoping at least one if not both or these are right:
a) Горный хребет растянулся через великих низменностях.
b) Горный хребет растянулся по большим низменностям.

I thought going to "cherez" from "po" might fix the problem as then I can use prepositional?? Thanks a lot for your help also
Your 2nd version definitely looks better, but I would put it as "Горный хребет растянулся через большие низменности." Note that the Prepositional case is called its way not because it's used with any preposition but because it can't be used without any. In your case, "через" requires Accusative.