Look for the map encounters that are labeled as "key incidents" when you hover your cursor over them. Completing all of them will make the final one appear which will lead to one of several endings that depend on what has happened in the city. Key incidents will not appear if your popularity points (musical notes) are too low. A fast way to finish the game is to place lots of structures that generate favors (green banners) which can be used to repeat encounters or create new key incidents early if you qualify for them.