Cartography (Ailsion Supplement)
From D&D Wiki
Knowing the shape and geographic nature of your campaign's setting can assist you in deciding where to travel, how to get there, or to help add flavor and depth to a session.
The Known World
The area in the NorthWest is the most prominently detailed here on D&D Wiki.
A Dungeon Master looking to add to the world could have his party discover an unknown Continent, full of new races and wonderful places.