I want the Arctic Explorer achievement but, best I can tell, I've explored every part of every map in Three Horns (divide/valley), The Fridge and Tundra Express.
Are there some other "arctic" maps like Southern Shelf included in this? I'm puzzled as to how I am missing this one. All the maps appear to be 100% filled in unless there are some "named locations" which don't leave gaps in the map when undiscovered or they're on some distant map I haven't checked (I think I have checked all of the maps you can fast travel to.)