Based on official specifications and security standards, any version of Cities: Skylines
In the world of PC gaming, Cities: Skylines (2015) stands as a monolith of simulation complexity. The base game, without any expansions or custom assets, occupies roughly 4 GB of storage. Once you add the myriad DLCs— Mass Transit , Industries , Parklife , Sunset Harbor , Airports , Plazas & Promenades —and a handful of community-created assets, the footprint regularly balloons to 15–30 GB. A heavily modded installation with custom maps, LUTs, and thousands of assets can exceed 50 GB.
: If you are looking for smaller downloads due to data limits, only use well-known, community-vetted repackers (like FitGirl or DODI), though even their versions will be significantly larger than 500MB because they preserve game integrity. Cities: Skylines that might naturally have a smaller file size?
While data compression is real, shrinking a 5 GB game to 500MB (a 90% reduction
GOG.com sells DRM-free versions of the game. You can install only the base game v1.0 (which is roughly 3GB) and ignore all updates. This is the smallest legal playable version available.