Sigil, sometimes called 'the Cage' or 'the City of Doors', is The City at the center of the Multiverse. The city of doors has portals everywhere. It is also the seat of power for most all of the city's Factions. The city is shaped like a ring with the city itself nestled on the inside. Sigil is a dreary place where it often rains. It's shape gives the impression that a visitor is always walking uphill.
Sigil is located atop the Spire in the Outer Planes. It has the shape of a torus; the city itself is located on the inner surface of the ring. There is no sky, simply an all-pervasive light that waxes and wanes to create day and night. Sigil cannot be entered or exited save via portals; although this makes it quite safe from any would-be invader, it also makes it a prison of sorts for those not possessing a portal key. Thus, many call Sigil "The Bird Cage" or The Cage. Though Sigil is commonly held to be located "at the center of the planes" (where it is positioned atop the infinitely tall Spire), some argue that this is impossible since the planes are infinite in all dimensions, and therefore there can never truly be a center to any of them, let alone all of them; thus, Sigil is of no special importance. Curiously, from the Outlands one can see Sigil atop the supposedly infinite Spire.
Sigil contains innumerable portals: any bounded opening (a doorway, an arch, a barrel hoop, a picture frame) could possibly be a portal to another plane, or to another point in Sigil itself. Thus, the city is a paradox: it touches all planes at once, yet ultimately belongs to none; from these characteristics it draws its other name: The City of Doors.
Sigil is divided into six districts, called wards:
- The Hive Ward, the slum and the ghetto, home to the poor, the rogues, and the unwanted dregs of the city.
- The Lower Ward, an industrial district, clogged up with the smoke from the foundries and from the portals to the Lower Planes.
- The Clerk's Ward, an affluent district, home to most of the city's lower-rung bureaucrats and middlemen.
- The Market Ward and Guildhall Ward are the home to the traders, craftsmen, artisans, guild members and other members of the middle class.
- The Lady's Ward, the richest and most exclusive section of the city, is home to the elites of society and of its government.