LongestRoad Sigil
Sigil, the "City of Doors", 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 has no dominant style of architecture or culture; it is quite the mish-mash. Its inhabitants are much the same. While petty crimes are not really punished, major unrest is quelled by the Lady of Pain and her task forces. Some sections of Sigil have their own resident-manned guard patrols to make sure the Lady doesn't even need to come by. (She is scary.)
Notable Places
Struquin's House: Not quite as nice as his first house (Which was burned down by some demons), but it's a pretty nice townhouse in a nice neighborhood. Three floors, master suite, running water, guest rooms, a formal dining room and a well appointed kitchen, as well as an office and a sitting room. The wine cellar is a little small, and not as well stocked as in his old house, but Struquin is planning to rebuild his collection so he can entertain properly.
The Fork Shop: They actually possess planar tuning forks, and offer a few of them for sale: though not for money. The shop owner is far more interested in curiosities: hope and dreams, memories, experiences. A half-celestial paladin of Virton's first kiss. Things like that.
Bahamut's Temple: Hidden under layers of illusion and such, the divine magic of this temple seems to be, well, not broken at least. Important people here included High Priest Saynith, who speaks only in parable to non-gods; and his Aide Marokhesh, who has a pretty awesome scrying bowl.
The Palace: Where the Lady of Pain supposedly dwells, though few people actually see her. All the nobility of note have at least small quarters here.
The Labyrinth: Exists beneath the Palace, accessible only by portal, the Labyrinth is an ever-changing series of caves that is never quite the same whenever you enter it. It's rumored to have fantastic treasure... and a lot of dead adventurers.
That Temple with All the Spikes: Devoted to the worship of some demon lord or other. Creepy.
Notable People
Joom: One of Struquin's peeps, deals in specialty items for rare races.
Kira: A really hot woman who seems to show up at Struquin's house wearing ribbons tied in a bow.