Squirrel Cage Jail in Counsel Bluffs. Admmition is $7 and they don't mind if you take photos, odds are you'll be the only one there. http://www.thehistoricalsociety.org/Jail.htm
Yeah I have been there a few times....I thought it was neat to hear how the inmates would take cigarettes and paper towels to burn their names into the paint (many which you can still see). The solitary confinement must have been rough. You can stand inside it but there isn't even enough space to squat down or sit. I can imagine that your legs would get very tired.