The Known World

The World is a vast place, yet since the fall of Nerath most of the knowledge about it is scarce. Most maps and records of all sorts were lost in the chaos that followed the demise of that nation. According to the surviving records, Nerath was the last great empire of the World, and it encompassed most of what historians call "the known world". However, currently there is only one official map of the lands of Nerath, which is limited to empire’s main regions and their eastern borders—what some people may call the "civilized lands". (CoN, p.3; CoN, map; DR385, p.78; DR393, p.12; DU155, p.31) Of what little information we have, we know that the Nerathi Empire spawned two continents. These continents were also home of at least four ancient empires that existed many centuries (or even millennia) before the founding of Nerath: Arkhosia, Bael Turath, Mira and Zannad. The continent where the heartlands of Nerath are located has been called "Nerath" in the game, yet that name is unofficial. The continent located to the east of Nerath is named Selduria. Between Nerath and Selduria lies a huge island named Kelarnil. (CoN, map; DR393, p.12; DR, p.90; DU158, p.86)
There is a third continent in the world, however, and Nerath may have had a few settlements there as well. It's existence is hinted at in the adventure "The Tariff of Relkingham" (DU158), which takes place in a town near a "land bridge between two large continents". There is no such land bridge in the official map from the "Conquest of Nerath" board game, meaning there is an unnamed, unmapped and unknown third continent to the west of the Nerathi continent.
The lands of the "known world" are surrounded by many seas. Between Nerath and Selduria we have 9 seas, 8 of them known as the "Eight Seas of the Iron Circle". Those are the Amilian Sea, the Midnight Sea, the Sea of Dragons, the Sea of Gnashing Ice, the Sea of Ghosts, the Sea of Mist, the Solannin Sea, the Sunrise Sea, and the Wailing Sea. Those are easily identifiable in the official map. (CoN, map; DR412, p.5)
There are three other seas named in official products that are not located in the official map. The Starfall Sea, the Frozen Sea and the Sunset Sea, but we have little information about them and so their locations are unknown. For what little we know, the Sunset Sea may be located in the southern edge of the Nerathi Continent, beyond the uncharted Desert of Desolation, as it was once part of Arkhosia, in a region known to be the "edge of the world". This can also mean that the south pole of the World is a hot place, unlike the north pole. The Frozen Sea is located in the northern hemisphere. This cold stretch of ocean pounds along the Frozen Coast, and flows near thin cracks in reality that connect the natural world to the Elemental Chaos. (DrCD, p.134; RotG; UA, “The Decaying Mansion of Memories”)