I was curious too! "The historic Preston Castle in Ione, California, was staged as a mental institution for the third episode."
http://en.wikipedia.org/wiki/The_Great_Escape_%28U.S._TV_series%29
A bit of a late response, but I did want to make note that Preston Castle was a boys reform school as a way to keep them out of San Quentin prison and Folsom prison, not a mental institution. My mom used to work at Ione Junior High, the town that Preston Castle is located. The place is fantastic and I strongly recommend visiting it if you ever get the chance.
shareI lived in Amador County for 7 years. I always wanted to take a trip inside this castle, but never got the chance before I moved. Get a "Moo Burger" at Mel's for me!
If any ghost hunters are interested, they have set up a live cam ghost feed streaming at all times. Simply click on Preston Castle Ghost Cam 1 or 2:
http://www.myachome.com/livecam
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