If you use the glitch were you permanently increase your acrobatics this cheat will take no time at all.

First you must jump out of any city in Cyrodill, if done correctly you should find yourself on a see-through surface with grass here and there (try jumping on the big ring shaped thing above the Arcane University garden, it seems to be the best).

Once you're on this weird surface run in the direction of the nearest off map realm and run.

After about 15 minutes you'll go off map. But, you will eventually fall and die so I recommend saving before attempting this cheat / glitch.