Warsong Hold in Borean Tundra is the main Horde base in Northrend.
The base was built by the Warsong Offensive when the Horde landed in Northrend as a headquaters to house the army. The base also houses the leader of the Warsong Offensive, Garrosh Hellscream.
Warsong Hold, Borean Tundra
The base also has a mine called Mightstone Quarry which has been ovenrun by the Undead Spiders called Nerub'ar.
There is a zeppelin Platform inside the fortress which goes to: