Produce specific Buildings
Throughout the course of Civilization VII, you can research technologies and civics that allow you to construct new buildings in your settlements. Sometimes, these buildings offer passive gold every turn after they are built.
Buildings such as the inn, bazaar, port, rail station, and others give the settlement they’re in gold every turn, which adds to the overall number in your treasury. You won’t be able to build all of these structures from the start of the game, but over time, your settlements can construct them all if you research the right technologies and civics. As such, it’s important to view every available technology and civic when you can research a new one to see exactly what they offer.