City gives +5 Gold per turn, and +20 commerce limit
Buildings and improvements:
Village (province improvement): +3 gold per turn
Farm (province improvement): +1 gold per turn, increases commerce limit by +15, +1 stability
Mine (province improvement): +1 gold per turn, decreases building costs in province by 10%
Lumbermill (province improvement): +1 gold per turn, decreases building costs in province by 10% (req. province with forests and smelting)
Windmill (province improvement): +10 commerce limit, -5% building costs, +1 gold per turn (req. machinery)
(All province improvements take 1 turn to build and cost 10 gold for first, 20 for second, 30 for third and so on. Multiple versions of the same can be built), and you can build more than one per turn
Forge: Decreases building costs in province by 10%, slightly increases troop quality, costs 60 gold, takes 1 turn to build, req. Smelting
Barracks: -20% recruitment costs for troops if all cities in empire have it, troops have slightly better quality, reduces upgrade costs, 80 gold, 1 turn, req. Warfare
Fishery: +10 commerce limit, +3 gold p/t, 30 gold, 1 turn, req. coastal
Port: Increases foreign trade yield by +1, stacks with all ports in empire, +5 gold p/t, 200 gold, 2 turns, req. Sailing
Market: +3 gold p/t, additional 1 gold p/t per resource owned, increases foreign trade capacity, 50 gold, 1 turn, req. Trade
Library: -20% tech costs if every city in empire has it, 50 gold, 2 turns, req. Writing
Alchemy lab: -40% tech costs if every city in empire has it, 100 gold, 2 turns, req. Alchemy
Money changer: +4 gold p/t, increases foreign trade, 90 gold, 1 turn, req. Currency
Inn: +2 gold p/t, increased foreign trade, important for events, attracts mercenaries and adventurers, 75 gold, 2 turns, req. Caravans
Tavern: +3 gold p/t, less unrests, important for events, attracts mercenaries and adventurers, 75 gold, 2 turns, req. Caravans
Temple: +2 stability, converts population, indirect religious effects, half cost under theocracy, 120 gold, 3 turns, req. Priesthood
Herbalist: +10 commerce limit, less disease events, troops heal faster, 40 gold, 1 turn, req. Herbalism
Courthouse: +2 stability, +6 stability if present in every city, -50% found city cost if present in every city, 120 gold, 2 turns, req. Code of Laws
Gambling house: +3 gold p/t, -1 stability, 80 gold, 2 turns, req. Currency
Tax Office: +1 gold p/t from villages in province, +1 gold p/t, -3 stability, 100 gold, 3 turns, req. Currency
Palisades: Better defense, 50 gold, 1 turn, no tech req.
Walls: Better defense, 100 gold, 2 turns, req. Masonry
Grand Walls: Better defense, 200 gold, 3 turns, req. Mathematics and Walls
Town watch: Extra militia troops when defending, 50 gold, 2 turns, req. Warfare
Dungeon: +1 stability, less war dissent, instability effects you less, 50 gold, 2 turns, req. Masonry
Theater: +4 stability, 150 gold, 2 turns
Sculptors Studio (Luch. only): +2 stability, at least one in empire needed to train basic golems, 50 gold, 1 turn, req. Arts
Carnivals (Bals. only) +2 gold, +2 stability, 60 gold, 1 turn
Most important, buildings affect events. You are less likely to get rebellion where you have herbalists and theaters than in underdeveloped town, even under low stability. Food from farm also helps. Also taverns and inns attract mercenaries and travelers, and even spies, and cities with dungeons quell dissenters better, as well as handle crooks.
Buildings that need to be present in every city have 3 levels: either they are present in every city, so that you get full benefit, or they are present in at least half cities, but not in every one, so you get half of their benefit, or they are present in less than one half of your cities, so you gain no benefit at all.
This is to make an incentive to keep down the number of cities and make a strategic decision – do I need one more city, to get extra commerce, or I'm better of small or more stable, so I'll put up a outpost or fort? This will also, I hope, encourage forts and outposts, and add more diversity, and also make it easier for me to keep track of all provinces