Four rivers extend out from the center, or separate into four sections, several locations which may be related to eachother through this symbol. Notably, the Land of Oz, The Garden of Eden or Paradise, and John Milton's description of Hell are all layed out in the same general pattern. The center of each is a special location, which in these examples are the Emerald City, The Garden and City of Eden, and the castle Pandemoneum, respecitvely.
Earth is also often separated into four directions, the four winds, or four corners kept by four watchmen or watchtowers, the four horsemen of the apocalyspe, and so on. This then may give reason for the comparison between earth and the underworld, hell, Oz, and Eden.