Recently I read the WoW insider article: that explains some easter eggs/fun bugs encountered in wow. In particular, I found this part very interesting:

There is one notable event for which we broke our unspoken rule of not reporting on exploits because it was just so damn bizarre: the Death Grip to end all Death Grips. Once upon a time, if a death knight stood on the ship from Booty Bay to Ratchet and Death Gripped someone, the Death Grip target would be hurtled clear across the world. He would land on a ship beneath the world, somewhere under Arathi, Alterac, or Hillsbrad. It was actually difficult to figure that out, because while you were hurtling beneath the world from one end of the continent to the other, your map would periodically stop functioning (likely because hurtling under the world at blinding speeds wasn't supposed to happen).
The author goes on to explain how he believes that Shatrath City is located above exodar, etc. So my question to you guys is do you have any idea into how Blizzard designs the world, ie. where the continents are relative to each other in the z-axis? Also how services like the zepplin/boats really work. Share what you know!