DESCRIPTION:
This glitch is harder to perform and may not always work.

1) Find any part of terrain that is more elevated than your character, and where your character can actually stand under.

2) Equip your mount and walk under the terrain.

3) The more tricky part: You need to jump AND unequip your mount at the same time. If successfull your character will clip trough the ground and fall down into oblivion. the only way to get out is to teleport to the nearest city.
You could also make the area teleporter active even below the ground so we could respawn above ground in a different area.