Uldaman

Uldaman is an old, earthen complex buried deep within the Khaz Mountains. It was partially excavated, but has since fallen into the hands of the Dark Irons, who find the place ideal to dig for earthly riches. Uldaman is one of the three known ancientTitan cities in the world, the two others being Uldum in southern Tanaris and Ulduar in the northern reaches of Northrend, located in the Storm Peaks.

History
From Blizzard's Official World Dungeons site:
 * Uldaman is an ancient Titan vault that has laid buried deep within the earth since the world's creation. Dwarven excavations have recently penetrated this forgotten city, releasing the Titans' first failed creations: the Troggs. Legends say that the Titans created troggs from stone. When they deemed the experiment a failure, the Titans locked the troggs away and tried again - resulting in the creation of the dwarven race. The secrets of the dwarves' creation are recorded on the fabled Discs of Norgannon - massive Titan artifacts that lie at the very bottom of the ancient city. Recently, the Dark Iron dwarves have launched a series of incursions into Uldaman, hoping to claim the discs for their fiery master, Ragnaros. However, protecting the buried city are several guardians - giant constructs of living stone that crush any hapless intruders they find. The Discs themselves are guarded by a massive, sapient Stonekeeper called Archaedas. Some rumors even suggest that the dwarves' stone-skinned ancestors, the earthen, still dwell deep within the city's hidden recesses.