I have walked the western border of Skyrim and it is either too steep to climb or at one point it say you can't go that way suggesting that is the border.
The Forgotten Vale is accessible through a cave through the mountains and appears to be quite a way passed the borderline.
The Forgotten Vale is a forgotten region of Skyrim once used by the http://www.uesp.net/wiki/Skyrim:Snow_Elf to worship the God http://www.uesp.net/wiki/Lore:Auri-El.
The Forgotten Vale is a forgotten region of Skyrim once used by the http://www.uesp.net/wiki/Skyrim:Snow_Elf to worship the God http://www.uesp.net/wiki/Lore:Auri-El.
Wasn't that hard to Google for it.
He asked if it was in game or just fan based/ uesp/ wiki and you pull up UESP and get all puffy at him. That makes sense.