Altered after the Seven Hour War
- Following the Seven Hour War and the surrender of Earth's governments, the Combine renamed the remaining cities with generic names and numbers, i.e. "City #". Each City would have a Citadel "stuck" in the middle of it, and there would also be Combine Overwatch forces garrisoned in each City to oversee the surrounding area, with the main City monitored by Civil Protection and City Scanners. The City would be damaged by the Combine to accommodate their needs with various technology.
- City 17 is the most notable Combine City, since it is there that Earth Administrator Wallace Breen elected to establish his Administration at some point after the Seven Hour War, there that Gordon Freeman reappeared 20 years after the Black Mesa Incident, and it is also where the uprising against the Combine started.
- As seen on the schedule found in the City 17 Trainstation waiting hall, Cities 8, 11, 12, 13, 15, 16, 24 and 27 are linked to City 17 by the railway.
- A City 14 is also mentioned by a Citizen in the City 17 Trainstation waiting hall: According to that Citizen, Breen has a presence there as well, likely through his Breencast broadcasts. For unknown reasons, City 14 is not present on the schedule in the Trainstation's waiting hall.
 Behind the scenes
City 40 and 49 are mentioned by Samuel in the story fragment Now Arriving: City 17 Vignette featured in Half-Life 2: Raising the Bar, in which he states that most of the towns are all identical from far and that only inside it is possible to see how they were "before" (i.e. before the Seven Hour War and the Combine occupation).
 List of appearances
- Half-Life 2 (First appearance)
- Half-Life 2: Raising the Bar
- Half-Life 2: Deathmatch (Non-canonical appearance)
- Half-Life 2: Episode One
- Half-Life 2: Episode Two
- The Final Hours of Portal 2