How do you run an RPG campaign in one city?

The city becomes a hub, not a setting

The usual failure is not underprepping a city; it is overprepping it the wrong way. A GM drafts a dozen districts, a guild for every trade, and a council with a dozen seats, then discovers the party only ever visits three streets. The rest sits unused, and worse, nothing in those three streets connects back to anything the party has already touched, so every session introduces new names instead of paying off old ones.

A city sustains a whole campaign the same way a good ensemble cast sustains a long-running show: a small, fixed set of places and people who keep returning, each carrying more history every time. Scope shrinks; depth grows.

Four things that make a city hold a campaign

Build these once, then spend every session deepening them rather than adding new ones:

• Three to five districts, not a map Pick districts the way you would pick locations for a settlement: each one earns its place by doing a job for the city (docks, markets, temple quarter, slums, the seat of power). Prepare each to the same shallow depth as a single settlement page. Do not draw streets between them; the party moves by scene, not by grid.
• A recurring cast of six to eight Fewer named NPCs than a sandbox campaign would use across a whole region, because the same few have to carry the whole campaign. Give each one a want, a district they are tied to, and at least one relationship to another NPC on the list, so pulling one thread moves a second person.
• Locations that change and stay changed When the party burns down the smugglers' warehouse, sinks a rival's ship, or gets a magistrate removed, that change has to still be true three sessions later. A city campaign proves itself is real by never quietly resetting a consequence the party caused.
• Secrets layered across the cast, not hidden in one NPC Instead of one villain holding one secret, split a single conspiracy across several of the recurring NPCs, each knowing a partial, plausible piece. Following any one lead should point toward someone else on the cast list rather than dead-ending or pointing somewhere new.

Resist the urge to add a new district

The strongest instinct to fight in a single-city campaign is reaching for a new location whenever a session runs short on material. A city with six well-worn districts and eight NPCs the players can predict the reactions of will outlast a city with fifteen thin ones. When a session needs fresh material, it almost always comes cheaper from an existing NPC's unresolved want than from a new street.

Keep a single page per district and per NPC listing only what has changed since the last time the party interacted with them. That page, not a map, is what makes the city legible six months into the campaign.

The city is ready to sustain a campaign when

Confirm before session one:

• You have three to five districts, each with a job the city needs done.
• You have six to eight named NPCs, each tied to a district and to at least one other NPC on the list.
• At least one past consequence the party could plausibly cause is written down as permanent, not resettable.
• A citywide secret is split across at least two NPCs rather than held by one.
• You can name what changes in a district if the party ignores it for a month of game time.