Location: Florence, Colo.
Ambiance: ADX is a federal prison designed to house prisoners who are considered uncontrollable in traditional facilities - many arrive here after killing or attempting to kill fellow prisoners or officers elsewhere. Most inmates are kept for at least 23 hours each day in solitary confinement. Cells are 7-foot by 12-foot concrete rooms with steel doors and tiny 4-inch by 4-foot windows that allow prisoners to see only a sliver of roof and sky.
Famous Guests: Current guests include "Unibomber" Theodore Kaczynski, "Shoe bomber" Richard Reid, Sept. 11 conspirator Zacarias Moussaoui and Salvatore "Sammy the Bull" Gravano, of the Gambino crime family.
Activities: Isolation is the name of the game at ADX, but as long as they're on their best behavior, residents can enjoy watching religious and educational programming on their own 13-inch black-and-white television set, or exercising alone one hour of the day in a separate concrete chamber.
Staff: Nearly 350 employees work to keep the 487 highly dangerous prisoners contained.
