Frostfangs

The Frostfangs are a mountain range in the far north of the continent of Westeros. The southern peaks and foothills extend into the North of the Seven Kingdoms, but the bulk of the range is located north of the Wall in wildling territory.

Season 1
Lord Commander Jeor Mormont of the Night's Watch has received intelligence suggesting that the wildlings under the command of Mance Rayder, the King-beyond-the-Wall, are gathering in the mountains for unknown reasons, and he intends to investigate what they are up to.

In the books
The Frostfangs extend from the Wall northwards into the Lands of Always Winter and the remote wildling kingdom of Thenn. They are jagged and hostile peaks, always covered in snow. The Skirling Pass is the most notable pass through the mountains, leading from the Haunted Forest to the Frozen Shore. Qhorin Halfhand, a ranger of the Night's Watch, is an experienced scout who knows the mountains and the pass almost as well as a wildling. Other passes include the Giant's Stair and the valley created by the passage of the Milkwater River. One of the tallest mountains in the range is the Forktop.

Behind the scenes
The production team felt that it was difficult and unsatisfying to realise the Frostfangs and other lands beyond the Wall with CGI or location shooting in Northern Ireland, so chose to film these sequences in Iceland, despite the practical problems this introduced with filming (such as expense and only having a few hours of light a day to film with).