So one time when I was driving west on the beltway and passed under the "Surrender Dorothy!" bridge, I said to myself that it didn't really look like the Emerald City so much as a cross between an alien spaceship and a fairy castle.
Which got me imagining all sorts of reasons there might be an alien castle there. This included thinking about military outposts in the Pacific during World War II and how they interacted with the natives.
And then John DeChancie invited me to submit a story to an anthology called Castle Fantastic, and I immediately knew what fantastic castle would be my inspiration.
I didn't want to make it too obvious, though, so I relocated it from the Maryland suburbs to a mountaintop in Pennsylvania, and wrote my story.
I think it's one of my better short science fiction stories, actually. I think John did, too. The anthology sold reasonably well, but attracted very little critical attention, so "The Garrison" went largely unnoticed, and has not attracted much in the way of reprints.
I did include it in Celestial Debris, though.
That's it; here's your list of handy exits: