When German reporter Marcus Hellwig was thrown into an Iranian prison on spying allegations, it struck him as odd that the chair in the interrogation cell had no backrest.
The reason soon became clear: "There was no backrest so that they could conveniently hit and kick people's backs," Hellwig told The Associated Press in his first interview with international media.
The 46-year-old reporter for Germany's mass-circulation Bild am Sonntag was arrested with his photographer after entering Iran on a tourist visa in October 2010 and interviewing the son of Sakineh Mohammadi Ashtiani, an Iranian woman sentenced to death by stoning for adultery in a case that generated international outrage.
Hellwig and photographer Jens Koch were split up and Hellwig said he was initially thrown into a plain 65 sq. foot (6 sq. meter) cell kept brightly lit 24 hours a day, but without a window or toilet. There was no furniture, only a carpet to lie on.
Hellwig said he was held in a facility run by the Pasdaran, Iran's feared Revolutionary Guard elite forces, and heard "terrifying cries" of inmates being abused every day.
"I was scared to death. Knowing that I was in a Pasdaran prison, with no lawyer or diplomatic assistance, outside of the official judicial system, they could have done anything to me," he said. "This total insecurity was the worst _ physical pain heals after a couple of hours."
Hellwig's book "Inshallah. Captive in Iran" _ using the Arabic for "God willing" _ is being released in German on Friday. There are no plans yet for an English edition.
He said his jailers kept constant pressure on him, initially taking him several times a day to the tiny interrogation cell, asking him the same questions, alleging at times that he was a spy or a terrorist _ which could carry a death sentence under Iranian law. He consistently told them that he was only a journalist, but they beat him and urged him to cooperate or endure more suffering, he said.
"They ask you nice questions and then ... all over sudden, boom, you get hit a first time, then comes the next hit _ it's all about breaking you," he said.
"They don't give you options, they give you the feeling they can do whatever they want."
Every day, except the Muslim holy day of Friday, Hellwig heard the cries of other inmates being tortured even more severely.
"It started in the morning with toned-down cries, then loud, terrifying cries," he said. "Never before in my entire life had I heard men capable of such cries."
In his book, Hellwig describes being tortured with electric shocks. In one instance, a prison guard forced him to sit on a steel table before he came back with a cart loaded with batteries and cables.
"The man comes very close to me with the cart, takes a cable and pulls it up to my lips. Then I pass out," Hellwig writes.
"A powerful shock goes through my body," he describes another torture scene. "There is a thunderbolt, it races through my jaw, spreads frantically over my scalp, than back into the ears. Thundering Pain."
In the interview, Hellwig said he still found the torture too difficult to talk about. "In the book I went as far and as close as I can without inflicting too much pain on myself," he said.
Judicial officials in Tehran could not be reached for comment on Hellwig's account. Human rights group Amnesty International says "torture and other abuses of prisoners are daily routine and go unpunished" in Iran.
Hellwig and photographer Koch _ who has not spoken to media since their release _ were eventually found guilty of committing unspecified acts against Iran's national security. But a court then threw out the journalists' 20-month prison sentence, commuting it to a $50,000 fine.
The two journalists were finally freed last year in February after German Foreign Minister Guido Westerwelle traveled to Tehran for a rare meeting with Iranian President Mahmoud Ahmadinejad, and brought the pair home on his government plane.
Iranian resistance groups cast Westerwelle's Tehran visit as a propaganda victory for the Iranian regime.
But Hellwig defended the German government, saying it made no compromises on human rights.
"Germany's foreign policy on Iran hasn't changed by an iota," Hellwig said. "Westerwelle discussed human rights violations with the Iranians during his talks."
After he got home to Berlin, Hellwig said it was difficult for him to return to his normal life after months in a cell in the western Iranian city of Tabriz.
"I had great difficulties coping with the speed of things and all the impressions here again," he said. "For some time, I couldn't even fall asleep without light."
For the time being, Hellwig said he has no intention of returning to Iran.
"Certainly not as long as the Mullahs rule the country," he said, referring to Iran's ruling Shia clerics. "Today I know what freedom really means."
Meanwhile, Ashtiani remains behind bars.
She was convicted of adultery in 2006 following the murder of her husband. In July 2010, Iran suspended plans to carry out her death sentence by stoning following the international outcry. Authorities said in December she may be hanged instead of stoned.