Sigil and the Outlands

The Outlands is the plane between the Outer Planes, a plane of neutrality, but not the neutrality of nothingness. Instead it incorporates a little of everything, keeping it all in a paradoxical balance—simultaneously concordant and in opposition. It is a broad region of varied terrain, with open prairies, towering mountains, and twisting, shallow rivers, strongly resembling an ordinary world of the Prime Material Plane.
The Outlands is circular, like a great wheel—in fact, those who envision the Outer Planes as a wheel point to the Outlands as proof, calling it a microcosm of the planes. That argument might be circular, however, for it is possible that the arrangement of the Outlands inspired the idea of the Great Wheel in the first place.
Around the outside edge of the circle, evenly spaced, are the gate-towns: sixteen settlements, each built around a portal leading to one of the Outer Planes. Each town shares many of the characteristics of the plane where its gate leads.

Gate-Towns of the Outlands

Town	Gate Destination
Excelsior	The Seven Heavens of Mount Celestia
Tradegate	The Twin Paradises of Bytopia
Ecstasy	The Blessed Fields of Elysium
Faunel	The Wilderness of The Beastlands
Sylvania	The Olympian Glades of Arborea
Glorium	The Heroic Domains of Ysgard
Xaos	The Ever-Changing Chaos of Limbo
Bedlam	the Windswept Depths of Pandemonium
Plague-Mort	The Infinite Layers of The Abyss
Curst	The Tarterian Depths of Carceri
Hopeless	The Gray Waste of Hades
Torch	The Bleak Eternity of Gehenna
Ribcage	The Nine Hells of Baator
Rigus	The Infinite Battlefield of Acheron
Automata	The Clockwork Nirvana of Mechanus
Fortitude	The Peaceable Kingdoms of Arcadia

Sigil, City of Doors

At the center of the Outlands, like the axle of the planar wheel, the Spire shoots impossibly high into the sky. Above this thin peak floats the ring-shaped city of Sigil, the City of Doors. This bustling planar metropolis holds countless portals to other planes and worlds. Creatures standing on one of Sigil’s streets can see the city curve up over their heads and — most disconcerting of all — the far side of the city directly overhead.
Sigil is a trader’s city. Goods, merchandise, and information come to it from across the planes. There is a brisk trade in information about the planes, in particular in the command words or items required for the operation of particular portals. These portal keys are highly sought after, and many travelers within the city are looking for a particular portal or a portal key to allow them to continue on their way.

The city is the domain of the inscrutable Lady of Pain, a being as old as gods and with purposes unknown to even the sages of her city. Is Sigil her prison? Is she the fallen creator of the multiverse? No one knows. Or if they do, they aren’t telling.

Type

Dimensional plane