Washington Post reporter Jason Rezaian says he had extraordinarily limited human interaction and spent 49 days in solitary confinement during his 18 months in an Iranian prison.
Rezaian is one of four Americans freed Saturday as part of a prison swap with Iran that came with the implementation of the nuclear agreement. He met face-to-face with senior Washington Post editors at the German hospital where he is recovering from his ordeal before returning to the United States.
"I want people to know that physically, I'm feeling good. I know people are eager to hear from me, but I want to process this for some time," Rezaian said.
He was picked up in 2014 and accused of spying – charges both the Post and the Obama administration called absurd. He was sentenced to an undisclosed prison term after a closed door trial in which he apparently was given little opportunity to offer a defense.
Rezaian said he spent most of his time in the custody of Iran's Revolutionary Guard – the military force tied to hardline religious leaders. He was kept in a small room with no mattress, and said walking around a courtyard was his only exercise.
FILE - An exterior view of Evin prison, which is thought to hold hundreds of political prisoners as well as regular inmates, in Tehran, Iran.
He was hospitalized three times with chronic eye and groin infections.
Rezaian said his last few hours in Iranian custody were among the most anxious, calling his departure from Iran and handover to Swiss officials as "touch and go until the last minute," fearing something would go wrong.
"I want to thank my family, especially the efforts of my brother Ali and my wife in Iran and my mother everywhere she was. They have been incredible," he said. "I also want to thank everybody at the Post and my colleagues in other media as well, as well as everybody in the U.S. government who played an important role in my release."
Also meeting with family Monday for the first time since his freedom from Iran was former U.S. Marine Amir Hekmati. His brother-in-law, sisters and Michigan Congressman Daniel Kildee visited Hekmati at the German hospital.
Hekmati, an Iranian-American, was arrested in 2011 on spying charges while visiting his grandmother.
FILE - In this video frame grab image made from the Iranian broadcaster IRIB TV, U.S. citizen Amir Mirzaei Hekmati, accused by Iran of spying for the CIA, sits in Tehran's revolutionary court, in Iran, Dec. 27, 2011.
An American pastor, Saeed Abedini, jailed in 2012 for spreading Christianity, and Nosratollah Khosravi-Roodsari, whose reasons for being in Iran are still unclear, also were freed Saturday.
Matthew Trevithick, detained in Iran last month on charges that were never disclosed, was freed in a deal separate from the four other Americans.
In return for freeing the four U.S. citizens, President Barack Obama offered clemency to seven Iranians who were either charged with or convicted of violating U.S. trade sanctions against Iran.
Charges include exporting military electronics to Iran and computer hacking.
The Obama administration also agreed to drop charges against 14 other Iranians outside the U.S. None is in U.S. custody, and officials have determined that efforts to have them extradited will not succeed.
Undated handout photo shows retired FBI agent Robert Levinson. His family received these photographs in April 2011.
Iran also has agreed to try to determine the fate of Robert Levinson, a former FBI agent who disappeared in Iran in 2007 while working on a project linked to the Central Intelligence Agency. U.S. officials have said they are not sure if he is still alive.
The Americans were freed as the United States and European Union lifted economic sanctions against Iran as part of last year's nuclear deal.
There was no mention of the prisoner swap while the deal was being negotiated. But Obama and other senior U.S. officials have said they repeatedly demanded that Iran free the Americans.