Monday, 26 September 2016
A historical novelist describes, e.g., London, Rome or Paris as they would have been in earlier centuries.
A fantasy author describes imaginary cities inhabited by exotic beings like wizards, trolls etc.
A science fiction writer may describe any of the above - rationalizing the wizardry or trollery if wants to remain within the bounds of sf instead of diverging into fantasy. He may also describe:
Paris in an alternative timeline (see here);
cities on Earth in the future (see here and here);
human cities on other planets in the future (see here);
alien cities (see here).
As Brian Aldiss remarked once, an sf writer works hard for his living.