A shape with a lion body and the head of a man. . . Throughout history, literature has combined pairing and place. Tom and Huck on the Mississippi River, Leopold and Molly in Dublin, the Ancient Mariner and the albatross in the Southern Ocean. In each of these, the place is so intertwined with the pair, at least in parts of the narrative, that it is indispensable.
Place can also provide an incidental richness and a tool to achieve other ends.
Clearly in Afghanistan. Afghanistan and St. Bart's are very real, which lends an air of authenticity to Sir Arthur Conan Doyle's story for a reader of any era, although other locations could probably have been substituted with minimal loss in credibility or entertainment value for his intended mass audience. More immediately in Conan Doyle's narrative, one outcome of the meeting was a decision by Holmes and Watson to share lodgings at one of the most famous addresses in all of fiction, 221B Baker Street . There is a Baker Street in London, but according to William S. Baring-Gould's The Annotated Sherlock Holmes , there was not a building numbered 221 until 1930, long after the demise of Holmes and the same year that Conan Doyle himself died. That anyone should spend such pains on such material was what surprised me.