Dibella's Watch adds an entire new continent to Oblivion. It comes complete with a major city, castles, towns, villages, farms, monasteries and all the good stuff that makes up a Medieval landscape. There's also fighting to be had and quests to be made!
Only for the ModDB page, here's the aerial shot of Dibella's Watch as of Beta 07.02. As you can see, there are new land areas in the west. These are still uncolonized in their entirety and aren't even marked on the in-game map as yet. You're welcome to visit though. You'll have to wait and see what I have in store for all that new land!