Speaking of places that weren't meant to be accessed...
I'll use links instead of messing up the forums this time.
Climbing Karazhan.
http://i2.photobucket.com/albums/y5/.../karahigh2.jpg
Above Ironforge, who HASN'T been here..
http://i2.photobucket.com/albums/y5/.../ironforge.jpg
Hopping over the blasted Lands wall beside the Dark Portal.. leads to Zul Gurub..
http://i2.photobucket.com/albums/y5/...69/WaytoZG.jpg
This is in Tristfal Glades, in the open inaccessible area west of Undercity.
http://i2.photobucket.com/albums/y5/...9/flatwall.jpg
This one is inside the Karazhan instance.
http://i2.photobucket.com/albums/y5/.../underkara.jpg
There's still a few places you can get too, the empty area in tristfal glades is still accessible, You can climb one of the walls and get passed the invisible wall in Hyjal Past allowing you to see the rest of the instance, gotta be an engineer, paladin or lucky with the noggenfoggers though. You can still get above Ironforge and under Stormwind too. Seriously I have nothing better to do so I just go out looking for hills to climb.
Edit: Too many smiley faces and not enough capitalization.