Cities: Skylines

The player starts with a plot of land – equivalent to a 2-by-2-kilometre (1.2 mi × 1.2 mi) area – along with an interchange exit from a nearby highway, access to a body of water, as well as a starting amount of in-game money. The player proceeds to add roads and residential, industrial and commercial zones, and basic services like power, water and sewage, to encourage residents to move in and supply them with jobs.

As the city grows beyond certain population tiers, the player unlocks new city improvements, including schools, fire stations, police stations, health care facilities and waste management systems, tax and government edicts, mass transit systems, and other features for managing the city. One such feature enables the player to designate parts of their city as districts. Each district can be configured by the player to restrict the types of developments permitted or to enforce specific regulations within the district's bounds, such as only allowing for industrial sectors devoted to agriculture, offering free public transportation for the district to reduce traffic, raising or reducing taxes for the various classes of development, or, with the Green Cities DLC, discouraging fossil-fuel vehicles from entering a district while not discouraging electric vehicles, reducing noise pollution caused by traffic.

Finnish developer Colossal Order, a thirteen-person studio at the time Cities: Skylines was released, had established its reputation with the Cities in Motion series, which primarily dealt with constructing transportation systems in pre-defined cities. They wanted to move from this into a larger city simulation like the SimCity franchise, and in preparation, developed Cities in Motion 2 using the Unity game engine to assure they had the capability to develop this larger effort. They pitched their ideas to their publisher, Paradox Interactive, but these initial pitches were focused on a political angle of managing a city rather than planning of it; the player would have been mayor of the city and set edicts and regulations to help their city grow. Paradox felt that these ideas did not present a strong enough case as to go up against the well-established SimCity, and had Colossal Order revise their approach.

The situation changed when the 2013 version of SimCity was released, and was critically panned due to several issues. Having gone back and forth with Colossal Order on the city simulation idea, Paradox used the market opportunity to greenlight the development of Cities: Skylines.

Upon release, Cities: Skylines received "generally positive" reception from critics, according to review aggregator Metacritic. IGN awarded the game a score of 8.5 and said "Don't expect exciting scenarios or random events, but do expect to be impressed by the scale and many moving parts of this city-builder." Destructoid gave the game a 9 out of 10 with the reviewer stating, "Cities: Skylines not only returns to the ideals which made the city-building genre so popular, it expands them. I enjoyed every minute I played this title, and the planning, building, and nurturing of my city brought forth imagination and creativity from me like few titles ever have." The Escapist gave Cities: Skylines a perfect score, noting its low price point and stated that despite a few minor flaws, it is "the finest city builder in over a decade."

Much critical comparison was drawn between SimCity and Cities: Skylines, with the former seen as the benchmark of the genre by many, including the CEO of Colossal Order. When the game was first announced, journalists perceived it as a competitor to the poorly received 2013 reboot of SimCity, describing it as "somewhat ... the antidote to Maxis' most recent effort with SimCity" and "out to satisfy where SimCity couldn't." A Eurogamer article touched upon "something of a size mismatch" between developer Colossal Order (then staffed by nine people) and Maxis, and their respective ambitions with Skylines and SimCity.

Paradox Interactive announced a sequel to Cities: Skylines in March 2023, titled Cities: Skylines II. The game was released on 24 October 2023 for Windows. The Xbox Series X/S and PlayStation 5 release was scheduled for Q2 of 2024, then postponed until October 2024 and was later indefinitely postponed.

A Lego-themed spin-off of the series, titled Lego Skylines, was announced at Gamescom in August 2026.