The idea of creating an artificial city sounds like something from the future. We'd be capable of it today if we put our minds to it, but it wouldn't be an easy job. It also wouldn't be an original idea. Someone did it 2200 years ago.
This is a picture of Nan Madol, which can be found close to Micronesia. Not a single shred of it is natural; the whole thing was built out of coral reef. We have no explanation as to how and why.