It is known as the Alcatraz of the Rockies. Built into a mountainside of Florence, Colorado, the Supermax prison is a notorious fortress-like jailhouse for America’s most dangerous criminals.

For Zacarias Moussaoui, the al Qaeda fantasist convicted for his role in the September 11 terrorist attacks, it will be home for the rest of his natural life.

He can look forward to a lifetime of solitary confinement in a facility that houses 399 other high security prisoners including former al Qaeda operatives, drug barons, and ganglords. Set in the middle of the desert and equipped with sophisticated surveillance technology, the prison is considered almost impossible to escape from.

Dubbed by the Guinness World Records as the most secure prison in the world, the 37 acre complex comprises four separate detention facilities, each with a different grade of security. Supermax is equipped with motion detectors, 1,400 steel remote-controlled steel doors, laser beams, barbed wire fences, pressure pads and attack dogs.

The prison opened in 1994 with the aim of incarcerating its inmates in solitary confinement for most of the day and keeping them in extreme conditions. The result is debilitating, say security officials, leading former prisoners to describe it as a living tomb.

Most of the prisoners are held in solitary confinement for 23 hours every day. For one hour each day they are allowed to exercise in a concrete chamber, fettered by leg irons and handcuffs. Prisoners stay in sound-proofed cells measuring seven feet by twelve. Each cell is bolted shut with a steel door.

Stark cells are lit by neon lighting and contain a bed, desk and stool. A shaft of natural light filters through a narrow slit window.

US security experts describe a highly-controlled environment designed to cut the prisoner off from the outside world and one another.

"They are in a security envelope, a security bubble. Their environment is sterile, they are isolated from the outside world and from the prison world," said James Aitken, a former US federal prison official.

"Moussaoui doesn’t know yet, but under such conditions as time goes by, they rot."

The psychological effect of long-term solitary confinement is profound, leading to prisoners suffering from hallucinations, anxiety, depression and self-harm. One former prisoner David Clark told The Guardian in 2002 of extreme restraint methods used by the prison, even during family visits.

"Your family has to look at you chained up like Hannibal Lecter or something. They have to look at you in pain, squirming," he said.

Human Rights Watch has described the conditions at such prisons as being a violation of international laws on civil and political rights as well as torture conventions.

Other inmates at the Florence Supermax facility include the British shoe bomber Richard Reid and the blind Egyptian Muslim cleric Omar Abdel-Rahman who was implicated in the 1993 terror attack on the World Trade Centre.

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