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!
Port Zerrva is where the player arrives on the island of Dibella's Watch. The town was inspired by Morrowind's Seyda Neen, actually.