There are three great cosmic regions, which can be successively transversed because they are linked together by a central axis. This axis, of course, passes through an "opening", a "hole"; it is through this hole that the gods descend to earth and the dead to the subterranean regions; it is through the same hole that the soul of the shaman in ecstasy can fly up or down in the course of his celestial or infernal journeys.

-Mircea Eliade