They’re not on any official maps, so I’ve been using Ser MountainGoat’s speculative map for Nunn’s Deep, et al:

And if you compare that to centers of mining as depicted in the (frankly not that great) maps from the WOIAF, it matches up pretty well:

It’s all in the north. And yeah, I think the plan was to let Tywin come in via the River Road as opposed to making him go by the Gold Road. If it was the latter, I would have put Lannisport under siege.