The CIA's chief interrogator called it "the closest thing he has seen to a dungeon."

At the agency's COBALT detention site in Afghanistan – also known as the "Salt Pit" – detainees were kept in total darkness, shackled to the floors or walls of their cells, and given buckets to dispose of their own waste. One senior interrogator later told the CIA's inspector general that a detainee "could go for days or weeks without anyone looking at him." Studies have concluded that such isolation has profound psychological impacts. It's no surprise the interrogator said detainees "cowered" whenever their cell doors were opened. Even though the Salt Pit was closed in 2004, the horrors that took place there stand as examples of the CIA program's inhumanity.

In a little-noticed section of the executive summary of the Senate torture report released in December, Senate investigators described how the Federal Bureau of Prisons, which runs the federal prison system, gave a green light to this dungeon.

In November 2002, just a few months after it opened, the CIA invited a BOP inspection team to assess the facility. During one of the multiple days of the BOP's inspection, a CIA officer ordered that detainee Gul Rahman be partially stripped, then shackled overnight to the concrete floor of his cell. Left naked except for a sweatshirt, Rahman died of apparent hypothermia at the end of the BOP's visit, though it is unclear whether anyone from the team actually saw him. After the inspection, the BOP team commented that they were "WOW'ed" and had "never been in a facility where individuals are so sensory deprived."

Despite seeing the conditions that led to Rahman's death, BOP apparently never urged the CIA to make the Salt Pit less like a medieval torture chamber. Instead, the BOP inspectors gave the prison their blessing, concluding that "the detainees were not being treated in humanely [sic]" and the "staff did not mistreat the detainee[s]." In the years that followed, more than half of the 119 victims of the CIA's Detention and Interrogation Program who were named in the Senate torture report spent time in the Salt Pit.

The BOP's rubber-stamping of the Salt Pit is perhaps the most shocking example of how a domestic prison agency helped foster U.S. torture abroad. But it is hardly the only one.

From solitary confinement to sexual abuse, the routine inhumanity of U.S. prisons can enable and normalize the use of torture abroad. Indeed, Charles Graner, ringleader of the Abu Ghraib scandal in Iraq, worked as a prison guard in Pennsylvania before joining his now-infamous Army Reserve unit. According to a 2004 Washington Post profile of Graner , the prison where he worked was rife with accusations that other guards engaged in brutal abuse: beating prisoners, spitting in their food, using racial epithets, and using one beaten prisoner's blood to write the letters "KKK." It was here, just south of Pittsburgh, where Graner first lost his moral compass. By the time he shipped out to Abu Ghraib, Graner was so entrenched in these daily realities that he reportedly whistled, laughed, and sang while abusing those in his custody.

Some international human rights bodies see the connection. In a recent review of U.S. compliance with the Convention Against Torture, for example, the United Nations simultaneously condemned both the U.S.'s failure to hold anyone responsible for CIA torture and the widespread use of solitary confinement in U.S. prisons.

Today the ACLU is submitting a Freedom of Information Act request to BOP to find out more about the agency's 2002 inspection of the Salt Pit. In the meantime, BOP officials – perhaps some of the same ones who signed off on the Salt Pit – march on with their own plans for a massive new prison that thumbs its nose at the U.N.'s Convention Against Torture report. The next federal prison to open will be ADX/USP Thomson in Northwestern, Illinois: A 1,600-cell Supermax prison devoted entirely to solitary confinement.

The resulting inhumanity will be all too predictable , even if BOP officials choose not to see it.