A city where the culture, religion and society revolve around gaming and gambling of all sorts, with racecourses and casinos of all types to be found everywhere.
Maze City, in which the entire surface - and much of the area beneath it - is a massive maze cut into solid rock. Wrong turns could lead into hostile temples, gravesite areas, disease-filled garbage dump areas, etc. A magic item here could include something that cuts new maze passageways, allowing for expansion. This could be located on a mesa or mountain, perhaps along a major trading road.
A city whose culture is devoted to raising and smoking marijuana. These peaceful and generous stoners do not have many physical resources or items to trade besides their huge surplus marijuana crops grown in outlying fields, perhaps by magical means. Perhaps their magic item is a huge greenhouse area, or magic items that help with farming and plant growth. There may be a very profitable, though illegal, demand for their crop in some other nearby cities or states. If players spend enough time there they will learn that these people have much in the way of strange druidic tradition and spellcasting and a great deal of magical knowledge, largely taken for granted. Weird, minor magical items are common, as are strange and esoteric spells. While these people are very pleasant, they are not very interested in trading; they would rather just smoke marijuana. They can easily be interested, though, with such items as unusual foodstuffs or kaleidoscopes, or unusual artwork or even storytellers whose art they find interesting and engaging.
A city where the people worship their bodily functions and seek to have diarrhea and other conditions as often and as strongly as possible. In this society it is considered to be very rude to eat in front of people or in social settings, but reliving one's colon or bladder is a social event - the reverse of how eating and going to the bathroom are in most cultures. People eat in small, secluded rooms; instead of shared dining areas they have large multi-person toilet areas where social events are held. Food and water supplies there will leave PCs dangerously ill for days. It would be an amusing but unpleasant place for PCs, but they might obtain spells or items that discomfort or disable enemies with sudden bursts of diarrhea at bad moments. They also might find that mundane commodities such as clay (for making toilets or tile) are rare and desired there, while items coveted elsewhere like gold and silver are discarded (because they make for cold, uncomfortable toilet seats). In fact, gold and silver and jewels might be commonly discarded into the sewers, by children in particular, and one adventure might involve PCs trying to figure out how to retreive gold and jewels from the disgusting, disease and creature ridden sewers - a place that locals hold taboo and that cannot be entered without severe punishment if one is caught.
A very ancient city in which concentric circles alternate between city areas and graveyard areas. The older graveyard areas could be taboo; local officials discourage or outlaw entry into them, but the grave complexes hold many treasures and monsters such as undead and rakshasta. Magic item could be something that keeps those monsters in the graveyard areas.
A city in the desert whose magic item creates many wells of cold water, the export of which allows for many other desert communities to exist - and those communities would die if the supply were disrupted.
A city built in the ruins of a simple home of a member of an immense, extinct ultragiant race. This fact might be unknown to the inhabitants, but figuring it out would be necessary for the PCs to solve part of their campaign. The magic item, unknown to these people, could be something small to the ultragiant but huge to the party such as a hairpin or needle or ring, something that could only be recognized as such if mapped or viewed at a particular angle from high in the air. Perhaps it could be the ultragiant's wristwatch, stiill mysteriously (to the locals) functioning.
A city where everything is made of fragile but beautiful shiny white china. Horses and metal items would not be allowed within its walls. Magic there might include local priests who can repair just about anything including the fragile china homes, or something that makes the china city walls impenetrable.
A city of disgustingly obese and voracious fat people who eat and eat and eat. Perhaps a nearby agrarian community profits handsomely from this place and players could eventually discover that a magical item (or group of them) brought into the city by those agrarians causes the voracious appetites and resulting obesity.
A city of bridges - perhaps a huge lake covered and criss-crossed with bridges, some narrow, some with shops and buildings on them like the old London Bridge. Perhaps it once was like Venice but everything sank except the bridges, or the water rose. Flying carpets would be at a premium here.
A city protected by a perpetual tornado or cyclone, created by a magic item and controlled by the city's wizard overseers.
A city where money and coinage are forbidden under penalty of death. Perhaps trade is only allowed in the form of barter or magic or favors to be repaid later.
A crime-ridden city filled with thievery, prostitution, robbery, murder, kidnapping, rape and assaults. Survival of the fittest would be the order of the day; the strong would rule and the weak would suffer. Criminals and psychopaths from all over the continent would be drawn to this place. It would be very dangerous but potentially very lucrative. A party in which no one spoke Thieves' Cant would be in trouble. Perhaps the players go here to rescue someone or to retrieve a specific item. Perhaps a magic item there causes psychopathy or anger or disregard for the law.
A huge, sprawling city in which chutes and updrafts of curved air provide quick and safe transport over long distances between buildings and districts. This of course could be the product of some magical artifact or presence.
