The Big Red Cheese said he was from Fawcet City, no?
Yes. This online
Atlas of the DCU is based on the old DCURPG Atlas and the Secret Files comics, with some recent additions. It places Fawcett City on Lake Michigan, east of Gary, IN.
What are the other fake cities?
Let's see, there's:
Fawcett City (Captain Marvel)
Gotham City (Batman)
Metropolis (Superman)
Central City (Flash; sister city of Keystone City in Post-Crisis continuity)
Keystone City (Golden Age Flash; sister city of Central City in Post-Crisis continuity)
Hub City (The Question; very corrupt)
Coast City (Green Lantern; destroyed by the Cyborg and now reborn)
Opal City (Starman)
Civic City (original JSA headquarters)
St. Roch (Hawkman)
Blue Valley (Kid Flash and later Star-Spangled Kid/Stargirl)
Gateway City (Wonder Woman under John Byrne)
Vanity City (Aztek)
Blüdhaven (Nightwing; I hate this name, in case anyone cares)
Star City (Green Arrow)
Midway City (Doom Patrol)
Quad Cities (Wild Dog; I think I'm the only person who actually liked this mini-series)
There are probably some more, especially from the Golden Age, that I am forgetting. During the GA, they created new cities at the drop of a hat!
Then you have the smaller towns like Ivy Town (where Ray Palmer taught college) and Happy Harbor (where the original JLA headquarters was) and Smallville.
The Absorbascon recently (in June, I think) did a series of posts on the various old "fictionopoleis" of the DCU and included several I'd never heard of before, like New Venice from some old Aquaman stories.