On this special page is an extensive exploration of how the Warcraft team designed the Northrend 5-man instance, Utgarde Keep in the Howling Fjord zone. First they delve into the story elements that ramp up to your introduction to the "impenetrable fortress in the side of a mountain." Upon arriving by boat to Daggercap Bay, you will see the damage wrought by the enormous, native Viking race and their proto-dragon mounts.
Overland quests from there will tell the story of how these Vrykul have used Utgarde Keep as a staging area to wage a battle against what they see as an invading force of Alliance and Horde.
The page goes on to explain other design decisions that will play out in Utgarde: as a "starter" dungeon, it's designed to be finished quickly; it will be more mission based due to the popularity of Old Hillsbrad and Black Morass in Burning Crusade; and you will get glimpses of the end boss before finally encountering him.