Right. First of all, I was a bit unsure wether to put this under exploits or exploration. However, since you don't really get any "advantages" doing this in the game, I placed it under exploration. Also, it's Karazhan, outdated.
Most of you probably already know about Netherspace, the so called "space" outside Karazhan. Quite a fun place really, some neat things to see.
Now, you can't do this method to go to chess or prince instantly, since the passage to get there is right before prince's room.
First off, the stairs after chess event leading up to prince, right before you get to the top, take a right and kill the Flesh crap that is wandering abouts. You should then be about here I don't black out my name because I just cant be arsed
Step 1, the positioning. NOTE: Does not work with a horse mount / undead mount, since they seem to be a bit smaller than other mounts. Chicken/bear works fine, didnt test others.
2. You should land about here.
3. Jump + tap foreward = get up here.
4. Jump wherever you want really (You might jump back into Kara tho, if you do, well.. Go back and try again. Note: use slow fall / iceblock / bubble or w/e to not die.
5. I jumped here.
6. Here I am "outside" the instanced kara. Quite eh fun place.
7. Fool around and you will eventually find this.
Not taking credit for the founding of Netherspace of course, but I didn't find anything about this way to get there.
I realise this is quite useless, however exploring is exploring, and this is one of the cooler parts of instance exploring there is imo. Also, you do have to clear up to and chess to get here, but still.. 2manable at 80 easily.
Enjoy, I suppose.