Geeks may know that Batman’s nemeses ended up in the Arkham Asylum for the Criminally Insane. True geeks know that Arkham Asylum was named after the Arkham Sanitarium in the works of influential horror author, H.P. Lovecraft. Über-geeks know that Arkham Sanitarium was based on the Danvers State Hospital in Danvers, Massachusetts (formerly Salem Village). From Danvers Asylum for the Criminally Insane:
Before long I was pretty nearly a devotee, and would listen for hours like a schoolboy to art theories and philosophic speculations wild enough to qualify him for the Danvers asylum. (“Pickman’s Model”)
I’ve heard personally of more’n one business or government man that’s disappeared there, and there’s loose talk of one who went crazy and is out at Danvers now. (“The Shadow Over Innsmouth”)
The first two NecronomiCons, a convention devoted to the Cthulhu Mythos and H.P. Lovecraft, took place at the Sheraton Tara Resort, about a mile north of the hospital. The eerie, Gothic towers of the hospital can be seen from the hotel. Michael Ramseur has written a lengthy article titled Danvers State Hospital: A Perverted Holy Place? which explores the history of this site.
(Kudos to Kent for out-geeking me with this bit of trivia.)