Just two hours outside of Denver, in a concrete pit among the Rocky Mountain foothills, sits the highest-security prison in America. Its official name is the U.S. Penitentiary Administrative Maximum Facility, but everyone calls it ADX. It’s home to the most dangerous criminals and escape-prone offenders in federal prison, including drug kingpin Joaquín "El Chapo" Guzmán, unabomber Ted Kaczynski, Oklahoma City bomber Terry Nichols, and World Trade Center bombers Zacarias Moussaoui and Ramzi Yousef. At other institutions, inmates are placed in solitary confinement for short stints in response to violent or aggressive behavior, but at ADX, inmates are confined to their 7X12 concrete cells 23 hours a day and receive their meals through a slot in the cell door. Their only glimpse of the outside world is through a thin slit of a window aimed at an empty sky. This deprives prisoners of learning the layout of the prison and the location of their cells. The only time inmates are allowed out of their cells is for an hour of exercise, where they're locked alone inside a caged pen. For the prisoners at ADX, they’re serving a life sentence in near-absolute isolation. Since ADX opened in 1994, there has not been a single successful escape.
