Layer Zero - The Core
In the core of the planet (above the God Machine) resides a flat land known as the Garden of Edena. Edena resides above the white sea (on the side where everything sinks).
Another flatland that resides in the core (below the God Machine) is that of Sheol. Sheol resides below the white sea (on the side where everything floats).
Between Edena and Sheol resides the God Machine.