The game features nine large maps to build upon; reaching population objectives open new areas in each map to expand into and unlocks new items. Map and asset editors are available to expand the content, and Cities: Skylines relies on Steam workshop for sharing maps and mods. The interface is fairly typical, offering icons for building-specific needs and map overlays for more detailed information. Unlike other city builders, zoning residential, commercial, and industrial areas is free, as the cost is incurred when placing roads, which automatically have areas to either side ready to be designated. It is easy to upgrade roads to larger or more quiet versions (noise pollution negatively affects residences), and raising road elevation is done using the page-up and page-down buttons, allowing for multi-level highway systems. Public transportation, power plants, water pumps and drains, garbage collection, health care (including cemeteries), fire protection, police, and education must all be managed. Areas of town can be designated as a special district, where unique laws and building specializations (taking advantage of natural resources such as timber or minerals) can be de defined. A sophisticated (and completely offline, by the way) simulation of citizens, their vehicles, their homes, and places of business runs under the hood, producing a very convincing reproduction of a town. Cities: Skylines is an extremely satisfying city builder that adds some notable unique improvements to the genre.