The Great Wheel

The most common understanding of these planes visualizes them as a group of concentric wheels, with the Material Plane at the centre. The Inner Planes form a wheel around the Material Plane, enveloped in the Ethereal Plane. Then the Outer Planes form another wheel around and behind (or above or below) that one, arranged according to alignment, with the Outlands linking them all.

Since the primary way of traveling from plane to plane is through magical portals, the spatial relationship between different planes is largely theoretical. No being in the multiverse can look down and see the planes arranged like a diagram in a book. No mortal can verify whether Mount Celestia is sandwiched between Bytopia and Arcadia; rather, this theoretical positioning is based on the philosophical shading among the three planes and the relative importance they give to law and good.