During a Justice League/Avengers crossover in the comics many years ago, it was cheekily suggested that DC Earth was actually slightly larger than Marvel Earth to accommodate all those extra cities. Really!
Which really shouldn't be necessary. Hard as it is to believe, only about 3% of the Earth's land area is permanently occupied by humans. And a lot of that is small towns and rural areas. So there's plenty of room to "plug in" extra large cities in places where there are only small towns today, like the Atlas of the DCU did with Metropolis and Gotham.
And let be noted that SMALLVILLE placed Metropolis in Kansas, only a few hours drive from Smallville, so this stuff tends to be variable.
And in the '70s, Smallville was assumed to be near the East Coast, like rural Pennsylvania or thereabouts, so it would be close to Metropolis. It wasn't until the Reeve movie that it was established as a Kansas town (though the radio series put the Kents' unnamed town in Iowa), while Metropolis in those movies was explicitly New York with its name changed (right down to having the Statue of Liberty). So Smallville was actually putting things back the way they'd been by moving Smallville and Metropolis close together again, albeit much further west.
In some comics and shows, Metropolis and Gotham are practically next-door to each other, yet I still remember one issue in which it was night-time in Gotham (so Batman could prowl the nocturnal city) at the same time that Superman was flying through a clear blue sky in Metropolis, so, wait, they were in different time zones?
(What was really happening, of course, is that the artist instinctively drew Batman operating after dark and Superman in bright daylight because setting the right mood was more important than worrying about time zones.)
That's nothing. In the DC Animated Universe's Gotham City, it seemed that the Moon was always full. (Man, that guy from the werewolf episode must've gotten really exhausted.) I think Gargoyles did the same thing.