The Fourth World has two twin planets, New Genesis and Apokolips. The two were once a single planet, Urgrund, but it was split after the time of the Old Gods, which ended with Ragnarok. New Genesis is a place that can only be described as heaven, populated by a peaceful, compassionate race of Gods and ruled benevolently by Highfather. Its mirror planet, Apokolips, rivals hell in despair and cruelty and is ruled by the Darkseid.
Several races inhabit the Fourth World but the dominant species is that of the New Gods, descendants of the Old Gods. They have evolved by being so near to The Source and so they see themselves as gods. They wield magnificent powers and have lived for centuries unknown to the general populace of Earth. To us they are giants, from ten feet to thousands of miles high. Their source of transportation that allows them to breach the dimensional rift is their Boom Tubes. When they die, their souls join the Source Wall, fortifying the barrier.