Michael Theodoulou writes for The National:
From grim experience, Maziar Bahari knows the fear that is probably gripping eight Iranian journalists who were arrested late last month and taken to Tehran's notorious Evin prison.
Mr Bahari was among the approximately 100 journalists detained in June 2009 during the tumult following president Mahmoud Ahmadinejad's disputed re-election.
The latest crackdown on reporters affiliated with reformist news outlets appears to be aimed at muzzling dissenting or independent voices, and suggests that as Iran gears up for its next presidential election in June, the regime's fears of unrest are escalating.
"My guess is they're all in solitary confinement," said Mr Bahari, an Iranian-Canadian journalist and filmmaker who spent 118 days in Evin, all but 11 of them alone in a small cell.
He suspects that they will be under extraordinary pressure, as he was, to confess that they were part of a western conspiracy to undermine the Islamic republic.
He says that he was beaten, slapped and kicked. As bad as that sounds, it was not the worst abuse he suffered.
"Solitary confinement leaves you with a feeling of utter despair and loneliness. It's the worst kind of torture," said Mr Bahari, 45.
"You don't know who's in charge of your life or what's going to happen to you. But you do know that you're in the hands of a government that has no respect for the law," Mr Bahari added. "And, of course, you know Evin's reputation."
The prison is located in a relatively affluent north Tehran suburb against the backdrop of the snow-covered Alborz mountains. Its picturesque setting belies its place in the dark corner of the Iranian psyche....
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Given the secrecy that shrouds Evin, human rights organisations cannot say exactly how many prisoners are held there. But one well-connected former political prisoner, who asked not to be identified, puts the number at about 6,000.
"Of these, about 300 to 400 are political prisoners, including between 30 and 50 women," the man said.
With dark humour, Iranians have dubbed the prison "Evin University" because most of its political prisoners are very well-educated.
Several Evin "alumni", like Mr Bahari, a former reporter for Newsweek magazine, have written harrowing accounts on their time there.
"The average level of education in Ward 209 [where political prisoners are held] is a master's degree," said Omid Memarian, an Iranian journalist and rights activist now based in New York.
He spent two weeks in Evin prison in 2004 after being forced to confess to false charges that he acted against national security.
Ward 209, named after its telephone extension number, is operated by Iran's Ministry of Intelligence, which is leading the latest crackdown on journalists.
Most of the ward's inmates are held in solitary confinement. The average cell there measures 2.2 metres by 1.7 metres and is equipped with a small washbasin but no toilet or bed, another former inmate said.
"One of the most serious problems in 209 and 240 is that the lights are on 24/7, so you can't sleep for more than three or four hours at a time," he said. "And you are blindfolded whenever you leave your cell."
Political prisoners still under interrogation are held in both wards. Once convicted and sentenced, most are moved to Ward 350, say rights activists and former prisoners.
This ward has communal cells and is run by prison authorities, rather than employees of the intelligence ministry or members of the Revolutionary Guards.
While no longer in solitary confinement, inmates in Ward 350 complain of other hardships, such as overcrowding, lack of adequate facilities and degrading treatment.
Despite the harsh conditions at Evin, Iranian authorities insist that conditions in the country's prisons meet international standards.
Responding to open letters of complaint smuggled out of Evin, an Iranian parliamentary delegation made a six-hour visit to the prison last month. One of the four MPs concluded conditions in Evin were better than those in US jails.
Another maintained Evin could hardly be called a prison because its facilities were so good.
"From now on, I will call it Hotel Evin," Safar Naeimi said. The quality of food there, he added, was better than he enjoyed at home.
His glowing appraisal drew a tart retort from a leading reformist politician held in Ward 350.
In an open letter, Mohsen Mirdamadi said that if Mr Naeimi was so impressed, he should check into the "hotel" for a stay to acquaint himself "with all its hidden aspects".
Ms Hashemi, the former president's daughter, was blunter.
The "tactless" reports by the parliamentary delegation were a mixture of "lies and delusion", she wrote in an open letter. Mr Naeimi treated the women prisoners he met "with contempt", she added.
As Iran's biggest jail for political prisoners, its very name evokes images of basement interrogation chambers and cramped, one-person cells.
Former inmates say the main problem at Evin is not the facilities, but human rights abuses such as solitary confinement, harsh interrogation tactics, and the denial of phone calls, family visits and access to their lawyers.
Another common complaint is that health care is often insufficient or even deliberately delayed or withheld as a means of pressuring political prisoners.