What is Mount Hyjal in World of Warcraft

Mount Hyjal will be one of the new zones in the upcoming expansion Cataclysm. It will have a brand new dungeon, Firelands. This dungeon will be both 5 man and 10/25 man dungeons.

Mount Hyjal was previously accessible to players, but later was closed off.

I will be controlled by three factions. They are The Black Dragonflight, The Guardians of Hyjal, and The Twilight's Hammer Clan.

Note: This information is considered sketchy at best as Blizzard may decide to change things before Cataclysm's release.