"I was barefoot in my pyjamas when they arrested me and it was really cold," says Sameer Jadala, a Palestinian school bus driver. "When I got to that place, they told me to strip and gave me a blue uniform. Then they gave me a black sack. They told me: 'This is your sack. You need to keep it with you. Any time someone comes to your cell, you must put it on your head. Any time they deliver the food, you must put it on your head. You must never see the soldiers' faces. You do not want to know what will happen if you take it off.' Sometimes I thought I would die in that place and no one would ever know."

Facility 1391 has been airbrushed from Israeli aerial photographs and purged from modern maps. Where once a police station was marked there is now a blank space. Sometimes even the road leading to it has been erased. But Israel's secret prison, inside an army intelligence base close to the main road between Hadera and Afula in northern Israel, is real enough. For 20 years or more it has been housed in a large, imposing, single-storey building designed by a British engineer, Sir Charles Taggart, during the 1930s as one of a series of garrison forts designed to contain growing unrest in Palestine. Today, the thick concrete walls and iron gates are themselves protected by a double fence overseen by watchtowers and patrolled by attack dogs.

situated on a secret military base. The base is used by the security services for various classified activities and thus its location is kept confidential."

But it is not just human rights lawyers and leftwing MPs who have a problem. Ami Ayalon is a former head of Israel's intelligence service, the Shin Bet. He was told about 1391 but says he refused to have anything to do with it. "I knew there was a facility not under the responsibility of the Shin Bet, but under the responsibility of the military. I didn't think then, and I don't think today, that such an institution should exist in a democracy," he says.

Sameer Jadala was detained at his home in Nablus last year at 3 o'clock on a December morning. For three days, the 33-year-old Palestinian was moved from one prison cell to another. On the fourth day, he was blindfolded, handcuffed and his feet manacled. Blacked-out glasses were pushed over his eyes as he was forced into the back of a car and on to the floor. Then he was covered with a blanket.

Jadala estimates that he was driven for about an hour. " We were taken out one by one. The only

The prison has held Lebanese abducted by the Israeli army as hostages, Iraqi defectors and a Syrian intelligence officer who tried to defect but was accused   of   spying and chose to remain in another prison rather than return home   and face a firing squad. More   recently,   scores   of Palestinians were incarcerated in 1391 for interrogation, which finally led to the almost accidental disclosure of a prison the state decreed did not exist.

Those who have been through its gates know it is no illusion. One former inmate has filed a lawsuit alleging that he was raped twice - once by a man and once with a stick - during questioning. But most of those who emerge say the real torture is the psychological impact of solitary confinement in filthy, blackened cells so poorly lit that inmates can barely see their own hands, and with no idea where they are or, in many cases, why they are there.

"Our main conclusion is that it exists to make torture possible - a   particular kind of torture that creates progressive states of dread, dependency, debility," says Manal Hazzan, a human rights lawyer   who helped expose the prison's existence. "The law gives the   army enough authority   already to hide prisoners, so why do they need a secret facility?"

Unlike any other Israeli prison, the International Red Cross, lawyers and members of the Israeli parliament have been refused access. One leftwing MP, Zahava Gal-On, describes Facility 1391 as "one of the signs of totalitarian regimes and of the third world". The Israeli government declines to discuss the secret prison other than to issue a standard response: "Facility 1391 is

reason I knew there were two other prisoners in the car was the sound of the chains," he says. "I was blindfolded right up to   the time they took me to the cell. There was a small slit in the door. It was not even   wide enough to push a cigarette through. A voice said, 'Take   the blindfold off but any time I come you   must   put it on and put your hands on the wall.' "

Raab Bader, a 38-year-old accountant and father of two, was also in the cells, although the two men had no contact. He too had been detained in Nablus, though he was convinced he had nothing to hide. " I was held like a blind mole, except for the prolonged hours that an [intelligence] agent interrogated me," he says.

Bader was variously told that he was on a submarine, in space or outside the borders of Israel. He was pushed into a windowless cell, 6ft square. A fan high in the ceiling drives air into the cell, but inmates say the noise is deafening.

"The cell walls were painted black. I never saw the ceiling. When I looked up, I saw only darkness. Light no stronger than the power of a candle penetrated in a peculiar way from one side of the room," he said in an affidavit.

The bed was a thin, damp mattress on a concrete slab a few inches above the ground. The toilet was a bucket, emptied every few days. Water to the cell came out of a hole in the wall, controlled by the guard. "On the ninth consecu tive day in the stench-filled cell, one of the soldiers was supposed to come and take me out. He almost vomited and rushed out of the cell," Bader says. "I spent many days in that solitary confinement cell and in others like it, and hour after hour I would talk to myself and feel that I was going crazy, or find myself laughing to myself."