Ziggurat
From WoWWiki
Ziggurats are Scourge structures found in Stratholme, the Eastern Plaguelands and the Ghostlands.
Background
The Ziggurat was the Scourge's and Forsaken's housing building in Warcraft III.
In real life, a Babylonian ziggurat is a temple tower of the ancient Mesopotamian valley and Iran, having the form of a terraced pyramid of successively receding stories.
Stratholme
In Stratholme, three ziggurats must be emptied before confronting Baron Rivendare. Each is guarded by a mini-boss:
Searching these ziggurats for Scourge Data is the objective for 
[60D] The Active Agent.
Eastern Plaguelands
In the Eastern Plaguelands, there are multiple ziggurats in the Plaguewood. Each is defended by a level 58 elite Ziggurat Protector. Destroying these ziggurats is the objective of the quest [58+] When Smokey Sings, I Get Violent.
Ghostlands
The Ghostlands of Quel'Thalas contain two named ziggurats: the Bleeding Ziggurat and the Howling Ziggurat, on either side of the Dead Scar. In addition, Deatholme contains minor ziggurats where Masophet the Black, one of Dar'Khan Drathir's lieutenants, can often be found. Dr. Whitherlimb, a Scourge scientist, can also be found at either the Bleeding or Howling Ziggurats or the ziggurats in Deatholme.
