If you are learning progression rules
Start with milestone and development-tree structure to understand how points, tiers, branches, and service access relate.
Milestones and Expansion Points Development tree tiers and branchesCities: Skylines II progression combines Milestones and service Development Trees. Milestones advance through Expansion Points earned passively from population and happiness changes and actively through city actions; their rewards include Development Points and access to services, policies, management options, and zone types. Development Points unlock additional options within trees, whose tiers and branches can require earlier nodes. This reference describes selected reported unlocks: mail sorting, parks, transport connections, college, parking, recycling, and water treatment. The sources also describe how the choices connect to city needs and operating costs. Exact node costs and a complete tree inventory are not provided here.

Start with milestone and development-tree structure to understand how points, tiers, branches, and service access relate.
Milestones and Expansion Points Development tree tiers and branchesRead the communications, parks, and college records for reported effects on mail, recreation, education, and employment options.
Post Sorting Facility Sports parks CollegeCompare the map-dependent water and train transport options with parking, recycling, and wastewater treatment functions.
Water transport Train transport Parking lots and garages Recycling Center Wastewater Treatment PlantChoose a topic to see how it works, where it helps and what to consider.
Milestones advance through Expansion Points earned from city growth and actions, and award Development Points alongside other rewards and unlocks.
Understand this choiceTrees expand unlocked services with options arranged in tiers and, for some services, branches; Development Points unlock further nodes.
Understand this choiceThe communications branch unlocks a post office and mailboxes, which the guide associates with increased citizen happiness.
Understand this choiceThe sports parks option unlocks affordable recreation choices that the guide says improve the city's recreation and entertainment rating.
Understand this choiceThe water transport node unlocks outside connections and waterborne cargo and passenger transport where the chosen map provides sea access.
Understand this choiceThe train node is presented as a transport-tree option for landlocked cities, while water transport is suggested for maps with sea access.
Understand this choiceCollege expands education beyond high school and is reported to support better-paying jobs, additional job types, resident happiness, and attraction.
Understand this choiceParking lots and garages provide parking areas, help manage road crowding, and generate some revenue through parking fees.
Understand this choiceA Recycling Center turns collected waste into materials that can be exported for additional money.
Understand this choiceThe Wastewater Treatment Plant treats wastewater to avoid polluting surface water sources, according to the official progression feature.
Understand this choiceThe official progression feature says points can be spent when received or saved for later; Shacknews also notes they are limited and advises against spending on an option with no current need.
Shacknews says water transport's value depends on sea access and recommends the train node for landlocked cities. It names several maps with sea access.
The sources describe college as expensive with upkeep, and IGN warns that building upgrades can be costly and strain the monthly budget. The sources do not give exact costs for the listed choices.
A source-bounded reference to Cities: Skylines II milestones, development-tree structure, and selected service, transport, education, parks, and communications unlocks. Records describe reported functions and constraints; they are not effectiveness rankings or a complete guide to the trees.
Explanations prepared with GPT-6 Luna and checked against the linked references. These are source-reviewed guides. They do not establish independently tested optimal builds or exact upgrade budgets. How coverage works.