This is a pretty fun little glitch where you can get outside of the walls in DTK, I discovered this on a Heroic run with some friends.
The location is in DTK past the stairs after King Dred, you must then go past the arch where you can't mount anymore, and go to the wall on the left in the far corner, do one jump half way up, and another then walk forward, you are then on thin air, you can walk around a bit, if you go to the right and to the ledge it puts you through the ground, make sure you have some form of slowfall, Flight Form does not work for you are still in the Instance. Once down have fun exploring a pretty good range around the instance except with no mobs, and its actually pretty cool, you can see the beginning blocks of northrend.
Have fun.![]()