In early 2003, two senior CIA officers arrived at the U.S. Embassy in Warsaw to pick up a pair of large cardboard boxes. Inside were bundles of cash totaling $15 million that had been flown from Germany via diplomatic pouch. The Americans and Poles then sealed an agreement that over the previous weeks had allowed the CIA the use of a secret prison - a remote villa in the Polish lake district - to interrogate al-Qaeda suspects. The Polish intelligence service received the money, and the CIA had a solid location for its newest covert operation, according to former agency officials who spoke on the condition of anonymity to discuss the interrogation program, including previously unreported details about the creation of the CIA's black sites," or secret prisons. The CIA prison in Poland was arguably the most important of all the black sites created by the agency after the Sept. 11, 2001, attacks. It was the first of a trio in Europe that housed the initial wave of accused Sept. 11 conspirators, and it was where Khalid Sheik Mohammed, the self-declared mastermind of the attacks, was waterboarded 183 times after his capture. In December, the European Court of Human Rights heard arguments that Poland violated international law and participated in torture by accommodating its American ally. "In the face of Polish and United States efforts to draw a veil over these abuses, the European Court of Human Rights now has an opportunity to break this conspiracy of silence and uphold the rule of law," said Amrit Singh, a lawyer with the Open Society Justice Initiative.