Building Settlements
In Starfinder, settlements are where characters can rest, recharge, retrain, and dedicate themselves to other downtime activities, all in relative peace. Traditionally, an adventuring band comes together in some kind of settlement, be it a small colony recently established on a moon in the Vast or a bustling continent-spanning city on the surface of a densely populated world. Some adventures take place entirely within a single settlement, while in others the party visits settlements only briefly between their adventures in space.
The first thing you should consider when building a settlement is its role in your story. Is this a major metropolis the heroes will visit again and again during their adventures? A backwater outpost where their adventures begin? The distant interstellar capital from which an evil tyrant issues cruel edicts? The settlement's campaign role will inform many of the other decisions you make about the place.
Once you know why you need the settlement, consider why it would exist in the setting. While established settlements certainly need access to sundries and supplies, local access to these resources are only necessary in low-tech or isolated outposts. Metropolises can even exist on worlds devoid of any naturally occurring food or water, although they're likely populated largely by creatures who don't need to eat or drink. These settlements need to be in such a valuable location that it offsets their need to import necessary supplies. While it might be easier to create a space station or city merely to serve the characters' needs, determining what function it has independent of the characters adds verisimilitude and can provide hooks for further stories.
Settlement stat blocks describe the components and traits of a settlement. You don't need to create a settlement stat block, but doing so can help flesh out the community you're building, and they can be a useful reference for your game.
Mapping a Settlement
Step 1. Layout: The layout of a settlement is as unique as the terrain upon which it's settled. In settlements developed before the advent of spaceflight, you might want to look at major trade routes likely developed alongside rivers. In more modern cities, this usually means looking at where the city's spaceport is located, likely near a body of water for emergency landings or where land would be cheap after the advent of spaceflight. The settlement might also use a structure like a space elevator, which likely makes its anchor a solid hub. If your settlement is a space station, build the central core and expand outward.
Step 2. Districts: Archaic settlements likely have a central district once defended by a wall. In some settlements, this area might be the most expensive part of town, filled with palaces and tourist districts, allowing guests a look at years gone by. If the settlement was established during or after an industrial revolution, the old town might very well be a run-down and polluted den of criminal activity. Districts often naturally develop as settlements grow into adjacent settlements, incorporating the smaller town or village into the larger settlement. These different wards often specialize over time into the dominant industry of the settlement, with residential districts typically replacing agrarian plots in postscarcity societies.
Step 3. Malls and Markets: Designate one or more open spaces in the settlement as a major commercial space. This marketplace typically grows in the city's downtown, often on the ground floor of office buildings or in large shopping malls. Mid-sized cities often develop these hearts of commerce in marketplaces and bazaars sometimes thousands of years old, using temporary stalls for local food and small businesses alongside large interstellar corporations in newly opened strip malls. This setup gives adventurers the flexibility to buy and deal in exotic and ill-gotten gains while still being able to reliably purchase mass-produced equipment from major manufacturers.
Step 4. Lodging: Heroes need a place to celebrate and recover between adventures. Bars, clubs, and restaurants make ideal locations to rest, introduce notable NPCs, and initiate quests. Unlike the medieval tavern, the hottest locations rarely have lodgings of their own but are often in districts featuring hotels or close enough to the spaceport that you can always save some credits bunking in the party's starship. Some cities feature alternative lodgings, ranging from sleeping pods and overnight cyber cafes to hostels and house rentals.
Step 5. Landmarks: To give your cities a sense of personality and local flavor, design a handful of iconic landmarks for the PCs to visit. Memorable names make these landmarks more interesting and can help hint toward future themes and story beats. A random stellar observatory might be noteworthy, but the Tapestry's Eye has an air of intrigue that could lead to a fun adventure hook.
Detailing Settlements
Beyond those basic details, the following considerations can help flesh out the settlements in your setting.
Location, Size, and Population
Populations ebb and flow due to a multitude of external factors. Advances in sanitation, medicine, and agriculture can spur dramatic population growth, while war, economic downturn, or plague can devastate it. A megacity has at least 10 million residents. Megaplexes formed of multiple megacities might have populations averaging 50 million or more. A multi-planetary alliance might have billions or more.
Population size is only part of the equation. Figuring out the ancestry ratios of that population and brainstorming how the members of various ancestries interact can often lead to interesting story ideas, or at least give you some jumping-off points when dreaming up how the settlement was founded and its later history.
Cultural Hallmarks
History
Economy and Political Stances
These resources can also affect political relationships. An area poor in a specific resource might have a strong trade relationship with another world that has it, or they might rely on conquest and war to plunder what they need! Settlements also disagree about political structures, public policy, religion, and any number of other factors.
You'll also want to consider the significant NPCs of each settlement. This includes the official rulers, but it also includes other major players, whether they act in an official capacity or entirely behind the scenes.