The ADX can house up to 500 prisoners in its eight units. Inmates spend their days in 12-by-7-foot cells with thick concrete walls and double sets of sliding metal doors (with solid exteriors, so prisoners can’t see one another). A single window, about three feet high but only four inches wide, offers a notched glimpse of sky and little else. Each cell has a sink-toilet combo and an automated shower, and prisoners sleep on concrete slabs topped with thin mattresses. Most cells also have televisions (with built-in radios), and inmates have access to books and periodicals, as well as certain arts-and-craft materials. Prisoners in the general population are allotted a maximum of 10 hours of exercise a week outside their cells, alternating between solo trips to an indoor “gym” (a windowless cell with a single chin-up bar) and group visits to the outdoor rec yard (where each prisoner nonetheless remains confined to an individual cage). All meals come through slots in the interior door, as does any face-to-face human interaction (with a guard or psychiatrist, chaplain or imam). The Amnesty report said that ADX prisoners “routinely go days with only a few words spoken to them.”

Robert Hood, the warden of the ADX from 2002 to 2005, told me that when he first arrived on the campus, he was struck by “the very stark environment,” unlike any other prison in which he ever worked or visited — no noise, no mess, no prisoners walking the hallways. When inmates complained to him, he would tell them, “This place is not designed for humanity,” he recalled. “When it’s 23 hours a day in a room with a slit of a window where you can’t even see the Rocky Mountains — let’s be candid here. It’s not designed for rehabilitation. Period. End of story.”

Hood was not trying to be cruel with such frankness. The ADX was built explicitly to house men often already serving multiple life sentences and thus facing little disincentive to, say, murder a guard or another prisoner. Still, during his own tenure, Hood said he made a point of developing one-on-one relationships with as many inmates as possible — he described Salvatore (Sammy the Bull) Gravano as “a very likable guy, believe it or not,” and he bonded with the Unabomber over their shared interest in running marathons — in hopes of eliciting good behavior in exchange for whatever he could do to make their sentences more bearable. But he also needed them to understand that even as warden, he lacked the authority to change the rules of their confinement. In the past, Hood has memorably described the ADX as “a clean version of hell.”