In the preface to one of her later novels (Passenger to Frankfurt), Agatha Christie revealed that the only thing she researched before writing was the location.

This makes sense--not only are there going to be some readers / viewers who are familiar with wherever you locate a story, but audiences love learning about places they don't know. If they learn that they've been handed a bill of goods about a particular location, they're not likely to be kind to the writer.

Everything else is semblance.