Gold and Shadows
Manifest Zones are those realms where reality is thinnest.
Eberron shares existence with a number of other planes of existence, alien realms that abide by different laws of what is physically possible. It is a commonly accepted model to imagine these other realms in some sort of invisible, elliptical orbit around Eberron, which brings each plane closer and farther away on (usually) predictable cycles. A plane’s metaphorical “proximity” to Eberron reflects its influence waxing and waning across the world. For example, when the dim plane of Mabar is close (or “coterminous” as the scholarly folk like to say to sound impressive), shadows grow deeper, lights don’t shine as brightly or as far as normal, and the dead have been known to become restless.
A manifest zone is like a semi-permanent tether between Eberron and one of the other planes… a localized area where the plane in question acts like it’s always coterminous in some way. A prime example of this is Sharn, a manifest zone that brushes shoulders with Syrania, the Azure Sky. The plane itself is inhabited by angels, and features a central city of clear-blue crystals floating in a vast expanse of noonday sky. Sharn, while perhaps a bit less lovely to look upon, shares the tendancy for vertical thinking and near-weightlessness. Magical means of flight work far more efficiently in and around the city, and the towers of the city rise impossibly high supported by magical-architectural wonders called Flying Buttresses that could never support such an immense weight of stone and iron and wood anywhere else in the world.
Manifest zones are among the best realms in the world for adventuring because by their very nature they defy the mundane. While a citizen of Sharn may be used to seeing someone float like a leaf from a high balcony and land with grace on a bridge below, the average resident of Fairhaven would consider that a miraculous sight. The larger-than-life events that can occur only in a manifest zone make then taylor-made for stories that will last the ages.