From A Wiki of Ice and Fire
The Frostfangs lie north of the Wall, just northwest of the Shadow Tower, separating the Lands of Always Winter to their west and the haunted forest to their east. Its southern peaks and foothills transition into the northern mountains, which are part of the North within the Seven Kingdoms. One of the largest mountains in the Frostfangs is called Forktop by the Night's Watch.
The easiest way into the Frostfangs is to follow the Milkwater river to its source, but this path is very visible from the Fist of the First Men. Other paths into the Frostfangs include the Giant's Stair and the Skirling Pass, if it is clear. 
The Frostfangs are a cruel and inhospitable wilderness of stone and ice, jagged peaks eternally covered in snow. However, the Frostfangs conceal a diverse series of wonders. Icy waterfalls plunge over sheer stone cliffs, mountain meadows are filled with grass and wildflowers, there are ravines so deep and black they seem to go all the way to hell, and bridges of natural stone span distances with only the sky to either side. 
Paths into the Frostfangs
A Clash of Kings
The Night's Watch send three scouting missions to search for Mance: one up the Giant's Stair under Jarman Buckwell, one to probe the Milkwater under Thoren Smallwood, and one into the Skirling Pass under Qhorin Halfhand.
In the Skirling Pass, Jon Snow and Stonesnake are sent ahead to dispatch with lookouts; they kill two and Jon captures a third, later releasing her rather than execute her. After discovering the free folk's location, the party turn back leaving Dalbridge to cover their retreat. Qhorin sends Ebben ahead on horseback, and Stonesnake afoot up the mountainside, then commands John to yield to the wildlings and do whatever is asked of him in order to gain their trust and learn what they are searching for. When the free folk finally overtake them, Jon yields as he was instructed and kills Qhorin.
A Storm of Swords
|“||The Frostfangs were as cruel as any place the gods had made, and as inimical to men. ||”|
|“||There's giants in the Frostfangs, and wargs, and worse things. ||”|
References and Notes
- ↑ 1.0 1.1 1.2 A Clash of Kings, Chapter 53, Jon.
- ↑ 2.0 2.1 2.2 2.3 A Clash of Kings, Chapter 34, Jon.
- ↑ 3.0 3.1 A Clash of Kings, Chapter 23, Jon.
- ↑ 4.0 4.1 A Clash of Kings, Chapter 43, Jon.
- ↑ A Clash of Kings, Chapter 51, Jon.
- ↑ A Clash of Kings, Chapter 68, Jon.
- ↑ A Storm of Swords, Chapter 7, Jon.
- ↑ A Storm of Swords, Chapter 15, Jon.
- ↑ A Clash of Kings, Chapter 51, Jon, p 538.