I used to drive by the Marion, IL prison (it's located just off I-57) on my way to Tennessee every couple of weeks or so.
At the time, the only criminal that I knew of that was doing time there was John Gotti, the "Teflon Don." He died there.
It's an imposing place - lit up at night like it's daytime. Smallish, not too big.
Maybe the cells are 6x6x8 - just large enough to sit up on your cot.