Robert King spent 29 years in prison in solitary confinement for a crime for which he was later cleared.
It was a dimly lit box, 9ft by 6ft, with bars at the front facing on to the bare cement walls of a long corridor. Inside was a narrow bed, a toilet, a fixed table and chair, and an air vent set into the back wall.
Some days I would pace up and down and from left to right for hours, counting to myself. I learned to know every inch of the cell. Maybe I looked crazy walking back and forth like some trapped animal, but I had no choice — I needed to feel in control of my space.
See also Atul Gawande's piece about solitary from the New Yorker last year.