As with most dimensions in Neptunia, Hyperdimension consists of four nations: Planeptune, Lastation, Lowee, and Leanbox. All of them, with the exception of Leanbox, reside on a single continent, which is surrounded by a vast ocean with nothing else as far as the eye can see. Leanbox stole cookies from the cookie jar and has been exiled to the island below the continent as punishment.
While the four nations are called nations, all games seem to imply that no less than 90% of all people live in the capital city of each nation, making them more like city-states. The map of Gamindustri reflects this too, with there being very few structures outside of the capitals, and even less urbanized areas.