When Buddhist systematizers took over the triple world they performed a quiet revolution: they redrew a geographical map as a psychological one. The three Buddhist realms, kamadhatu, rupadhatu and arupadhatu, are not earth, atmosphere and sky; they are desire, form and formlessness, and a being's location in them is a function of its mind. The realm of desire runs from the hells through animals, ghosts, humans and the six lower heavens, everything governed by the pull of the senses. Above it the realm of form holds the heavens reached by the four meditative absorptions: its gods have bodies and radiance but no hunger, no sex, and progressively less coarseness, because they are, in effect, states of concentration given an address.
The formless realm at the top, boundless space, boundless consciousness, nothingness, neither perception nor non-perception, abandons location almost entirely; its names are simply the names of the four formless attainments. The correspondence is exact and doctrinally deliberate: a meditator who attains an absorption in this life is reborn in the matching level after it, so cosmology becomes a mirror of contemplative attainment. The redrawn map serves the Buddhist argument that mind makes worlds; where the Vedic triad told you where things are, the Buddhist triad tells you what minds are like, and the same ancient word, trailokya, carries both.