geography and botany

If, for plot purposes, there are caves and cliffs in a region late in the book, it may be wise to actually introduce them sooner.

Perhaps I can get away with a brief mention in the already written stuff.  The hero's new supporting cast has a character who will definitely look into them.

And then in another story, I had thrown in peaches and then I started to wonder whether they were suitable for the milieu.  A fairytale one, where you often have pumpkins and turkeys where transportation is crude -- then the fairytale could explain where they came from -- and then a little more research reveals they were safely medieval.