First and foremost, credit for how to get under the world goes to Koalamo here: http://www.mmowned.com/forums/wow-ex...-northend.html
Yes I am aware this area is for a quest, but this is the outside view, so meh. When i first found it I didn't know it was a quest place.
So I flew towards Icecrown Citadel and here's what I found:
From just after the under IC entry point: Image of UnderIC Gate Structures - Photobucket - Video and Image Hosting
The first of two pillars: Image of UnderICC First Pillar - Photobucket - Video and Image Hosting
The top of the cave map: Image of UnderICC Cavetop - Photobucket - Video and Image Hosting
The lower pillar, which is comprised of huge needle like spires, like the one behind ZG, except way bigger: Image of UnderICC Second Pillar - Photobucket - Video and Image Hosting
What happens when you attempt to fly into ICC itself? You fall: Image of UnderICC Falling Cave - Photobucket - Video and Image Hosting
The location of the cave around the pillars is about halfway up the second pillar, on the north by northwest facing.