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!
Dibella's Watch is the land of small castles, local lords and minor villages. Here are some pics from the Shire of Wordham. Some landscape in Dibella's Watch is directly inspired by the Skyrim preview screenshots.