I'm not actually sure if this has been found out and said so on English websites because searching in Google came up with no results which I was looking for.
Anyway, onto the fun part...
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(Look in the top right for the co ords of where I am - I'm outside Icecrown Citadel for people with no co ords. Look on the radar for my where abouts). When you're at that point, go under the top bridge and look up. You should see a gap between the wall and the end of the brigde.
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Go through the gap and look to your left, you should see another gap between a door-like object and the wall. Go through that.
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After going through the gap, look down and go south a bit. (Go down further than I've showed on the picture).
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Look to your right and go towards the mountain.
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You should then see a part of the mountain missing which resembles a triangle.
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Once again, go through that gap and then go down quite a bit.
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You're under Northrend the Magixman way.
Also, I apologize for using Imageshack, I realise now that it's not the best option for some people like me. Keep refreshing if you can't see the image.