I've been invited to contribute to an anthology that requires all stories take place within a tightly constrained geographical location, though the stories can be set in the past or the present.
Though I visited this location a few times in the late 1980s and early 1990s, the story I'm writing takes place even earlier. And my protagonist has an occupation with which I have minimal knowledge.
So, I'm having to research both time and place. What did this location look like at that point in time? What was happening in the world that impacted that location? How did my protagonist's occupation fit the time and place? And so on.
I don't write much fiction that requires extensive research because it often isn't cost-effective, and I always find myself traveling down research dead-ends or spending time reading about cool stuff that has nothing to do with the story-in-progress. (Though, I must admit, my ghost story "Pushing Coal" in Specters in Coal Dust, for which I had to research coal mining in the 1950s, turned out pretty good.) This time is no different.
But I'm glad I'm doing it because this is a story I never would have written without the invitation, and I have high hopes for the final draft.