Prison in Colorado is the 'modern day Alcatraz' with incredibly strict rules and world's most notorious criminals

A prison in Colorado has earned the nickname of a 'modern day Alcatraz' while housing some of the most notorious criminals alive today.

Florence, Colorado attracts many tourists with its hot springs and renowned rafting opportunities, but just a few miles away from the wholesome activities and people taking selfies, there's a much darker side of town.

Prisoners are rarely allowed outside of their rooms. (JASON CONNOLLY/AFP via Getty Images)

USP Florence ADMAX – also known as the ADX or the 'Alcatraz of the Rockies' - is located in Fremont County and holds the title of the highest-security federal prison in the United States.

The prison was opened in 1994 and is categorized as a 'supermax' prison, where control is even greater than a maximum-security prison. It's opening came 30 years after the notorious Alcotraz prison in San Francisco was closed in 1963.

The facility is designed to hold inmates that pose extreme security threats, and as a result the likes of drug lord El Chapo, Boston bomber Dzhokhar Tsarnaev, and 9/11 conspirator Zacarias Moussaoui are among its residents.

Also housed in ADX are Ramzi Yousef, who was convicted in the 1994 World Trade Center bombing; shoe bomber Richard Reid, and Oklahoma City bombing conspirator Terry Nichols.

Much of the cell is made of concrete. (Lizzie Himmel/Sygma via Getty Images)

So, it's safe to say we don't want anyone breaking out from behind those walls.

Thankfully, the prison has a whole lot of devices and rules in place to help keep the convicts under control.

As well as motion detectors, cameras and remote-controlled steel doors inside the facility, it's surrounded by 12-foot tall razor wire fences and patrolled by heavily armed officers, laser beams and attack dogs.

According to Identiv, prisoners housed at ADX are prohibited from spending almost any time at all outside their cells, and have very little contact with other humans altogether.

In fact, for the first three years behind bars, prisoners are not allowed to come into contact with other prisoners at any time.

They mostly eat in their cells, though prisoners are able to eat in a shared dining room once they reach the last year of their sentences.

The prison is guarded by lasers and guard dogs. (Robert Daemmrich Photography Inc/Sygma via Getty Images)

Inmates can earn themselves more 'outside' time for good behavior - whatever that looks like for the world's worst criminals - though 'outside' is a pretty loose term for what actually happens.

Rather than getting some fresh air in a nice yard, prisoners actually go to a bigger cell with vaulted ceilings, which is reportedly dubbed the 'concrete pit' and is only large enough for a prisoner to walk 10 steps in a straight line.

Those who are particularly well behaved could earn themselves a transfer to a slightly less-secure prison, but chances of escape are limited further by the windows installed in the cells, which are designed to prevent inmates from knowing their location within the prison by only offering a view of the sky and roof.

With all of these rules and stipulations in place, plus the 24-hour supervision, there's no way prisoners can get out of ADX unless they get moved, or they manage to complete their sentence.