This is my first exploration thread, it's kind of useless but you can still do some fun things with it..
Here's how you do it, first get under Stormwind City, if you don't know how to do that look in other threads, you'll find it.
Once you're under, go to this spot on the map.
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Once you're there you're going want to go up this hill.
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Now get up and jump through the space between the castle and the wall, and get on the other side, careful not to fall.
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Once you're on the other side, you're going to have to wallclimb (sort of) so if you're a Druid, get into Cat Form, Shaman's get in Ghost Wolf. I've done it without Ghost Wolf so so can you. Jump and aim for this spot.
http://img177.imageshack.us/img177/7341/jumpherehw1.jpg
Once you jump (it might take a couple of try's) You should end up right here.
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You should jump up once and you'll land kind of in the air, like so.
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Once you get up you'll be up like this, just jump down.
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Once you're down go to the left of the giant pyramid in the middle, you'll find this hill, go up it.
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Make you're way up the hill, go to the very top, there will be a jump stand on it and face forward, drink you're noggenfogger (or Slow Fall, Levitate) and jump to the castle roof.
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Then there you go! You're on top of this roof, sort of useless, but you can shoot people if they're in range!
I'm going to keep exploring over here, I'll let you know if I find anything more useful.
Thanks for reading! Best of luck!