This is ADX, the maximum security prison where Joaquín "El Chapo" Guzmán and other feared criminals are

This is the photo of Ovidio Guzmán detained by the Mexican authorities 2:43

(CNN Spanish) --

When inmates arrive at the United States Penitentiary's Maximum-Administrative Center in Florence, Colorado, it is immediately clear: ADX, the most secure maximum-security prison in the country, is built to isolate them from the world.

And there Joaquín "El Chapo" Guzmán, one of the most wanted drug traffickers in Mexico for many years, pays his sentence.

Known as the "Alcatraz of the Rocky Mountains," this maximum-security prison is where America's most feared convicted criminals have landed.

It is built for the worst of the worst in the prison system, including the most violent inmates and convicted terrorists.

Many of the more than 400 inmates spend up to 23 hours a day alone in soundproof concrete cells measuring 2 by 3 meters.

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A former ADX warden once told CNN that imprisonment there is "far worse than death."

This is a look at the maximum security prison where Guzmán and other criminals are being held.

This photo taken on February 13, 2019 shows a view of the United States Penitentiary Administrative Maximum Facility, also known as ADX, in Florence, Colorado.

(Credit: JASON CONNOLLY/AFP via Getty Images)

A fortress in the middle of the mountains

At ADX, heavily armed patrols roam the sprawling complex.

A dozen imposing gun towers rise above brick buildings.

Walls topped with barbed wire partially block the snow-capped mountains.

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“As soon as they walk through the door … you see it in their faces,” former ADX director Robert Hood said.

“That's when it really hits you.

You are looking at the beauty of the Rocky Mountains in the background.

When you go inside, it will be the last time you will see him.”

“Supermax is the afterlife,” said Robert Hood, who served as ADX director from 2002 to 2005. “It's long term.

… In my opinion, it is much worse than death.”

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“As soon as they walk through the door…you see it in their faces,” Hood said.

“That's when it really hits them.

They are looking at the beauty of the Rocky Mountains in the background.

When they come in, it will be the last time they will see them."

Meals slide through little holes in the doors.

The bed is a concrete slab dressed with a thin mattress and blankets.

A single window about 106 centimeters high by 10 wide lets in some natural light, but is made so that inmates cannot see beyond the building.

The cells have immovable stools and desks made of concrete.

Solid walls prevent inmates from seeing other cells or having direct contact with other inmates.

“The architecture of the building is the control,” Hood said.

“He is designing so that the inmates cannot see the sky.

Intentionally.

They put cables so that the helicopters cannot land, ”he added.

• Ovidio Guzmán, son of Chapo Guzmán, is captured in an operation in Sinaloa

Inmates have little contact outside of prison guards and staff.

They must wear leg shackles, handcuffs and waist chains when taken out of their cells, and must be escorted by guards.

One hour of recreation is allowed in an outdoor cage slightly larger than the prison cells.

Inside the cage, only the sky is visible.

This photo taken on February 13, 2019 shows a view of the United States Penitentiary Administrative Maximum Facility, also known as ADX, in Florence, Colorado.

(Credit: JASON CONNOLLY/AFP via Getty Images)

Some inmates with whom El Chapo shares prison

Ted Kaczynski,

also known as the Unabomber, received multiple life sentences for mail bombings that killed three people and injured 23 others between 1978 and 1995.

Eric Robert Rudolph,

who is serving a life sentence for various attacks, including the 1996 bombing at Atlanta's Centennial Olympic Park during the Summer Olympics, which killed two people and injured more than 100.

Larry Hoover,

reputed leader of the Chicago Gangster Disciples street gang, who is serving 150 to 200 years for murder.

Terry Nichols,

who was found guilty of being an accessory to Timothy McVeigh in the 1995 Oklahoma City bombing that killed 168 people.

Judges sentenced him to life in prison in federal and state trials.

Matthew Hale,

the former leader of the white supremacist group World Church of the Creator, who was sentenced to 40 years in prison for trying to hire an undercover FBI informant to kill a federal court judge.

Ramzi Yousef,

who was convicted in 1998 for his role in organizing the 1993 World Trade Center bombing, which killed six people and injured more than 1,000.

He was sentenced to life in prison plus 240 years.

Dzhokhar Tsarnaev

who was sentenced to death for the April 2013 double bombings near the finish line of the Boston Marathon.

The shelling killed three people and injured more than 260.

-- With reporting from CNN's Ray Sanchez, Alexandra Field, Drew Griffin, James Polk. 

El Chapo Guzmán