Located just east of the Barrens on Kalimdor, Dustwallow Marsh is, as the name implies, made up of mostly swampland, with bases for both factions, and one neutral one, distributed around the area. Alliance players gain access to their base, Theramore, by use of a boat that sails from Menethil Harbor in the Eastern Kingdoms. Short of crossing the entire continent from Darnassus, this is the only way for Alliance players to get to this portion of the world.
The Horde have Brackenwall Village, which is actually run by ogres.
Arcaz Island is located off the coast, and is where the human king, Varian Wrynn was kept captive during his kidnapping in prior years. There are no quests or dungeons here, just naga and black dragons, which was an early clue of who the mastermind behind the kidnapping was.
A short time ago, a Goblin town called Mudsprocket was placed in the western part of the zone, and quest-givers here offer tasks for Horde and Alliance players alike.
A short distance from Mudsprocket is the imposing entrance to Onyxia's Lair, home of the cunning black dragon herself.