The problem with fake cities is that you need multiple writers developing the city’s locations, AND their successor writers honoring what came before. Gotham has this with places like Arkham Asylum, Ace Chemicals, the Iceberg Lounge, GCPD HQ, etc. It also has a very unifying theme of being very noir, Gothic, and run down. It makes the location feel alive in a way that no where else in the DCU does.

The only place that comes close is Metropolis, but the problem is not enough writers have built on what came before in regards to Metropolis. Other than the Daily Planet and the LexCorp HQ, there’s not really consistently reoccurring landmarks. Ace of Clubs bar should definitely be showing up more for example. And Metropolis is often drawn as a boring generic city that doesn’t at all live up to its title of the “City of Tomorrow”, but that’s on the artists for not putting in more effort.

Wanting Diana to have her own City is understandable, but unless effort is made to give that City an identity of its own with recognizable landmarks, something that requires multiple writers building on what came before rather than tossing everything out at the start of their run, you’re better off just picking a real City. Billy Batson for example has lost nothing from moving to Philadelphia from “Fawcett City”. Flash’s Central City could be Detroit and it would basically be the same. When was the last time GL showed up in Coast City in any meaningful way? Atlantis is usually the focus of Aquaman so it has that going for it at least. You could even have a real City get the nickname “Gateway” just like how in GA Rebirth, Seattle temporarily was renamed “Star City”.