A high security prison that's been open for almost 30 years has had zero successful escape attempts.
Depending on a person's crimes, they may be deemed too dangerous and uncontrollable to be held in a normal prison.
With this in mind, they have to be placed in a high security prison instead.
One of the most famous prisons like this was Alcatraz in San Francisco, which closed its doors in 1963.
Advert
While it was up and running, the notoriously strict prison housed the likes of Al Capone and Meyer Harris Cohen.
Three inmates, brothers John and Clarence Anglin and fellow prisoner Frank Morris, managed to break out of the high security prison the year before its closure.
The trio were never found, but were presumed to have drowned as Alcatraz was located on an island off of San Francisco Bay.
Advert
Following Alcatraz's closure, ADX Florence went on to open its doors in 1995 and is now the USA's only maximum security prison.
Some of the biggest modern day criminals are currently held at the Colorado-based prison, including Mexican drug kingpin 'El Chapo' (real name Joaquin Guzman-Loera), shoe bomber Richard Reid, and Boston Marathon bomber Dzhokhar Tsarnaev.
It's reported inmates house at ADX Florence spend 23 hours of the day in their tiny cells.
Advert
According to the New York Times, the cells are just seven-by-12-foot (two-by-four-meters) in size and are made up of concrete. The rooms are also said to be soundproof.
Unlike other prisons, the likes of El Chapo - who has previously escaped from Mexican prisons twice - won't meet up in a dining room for their meals; instead they have their meals given to them through a slot through their cell door.
The sunlight they get is very limited too as, aside from having just one hour outside their cells a day, prisoners only have a slit of a window in their cells.
Advert
While Alacatraz had 14 escape attempts during its 29-year run, ADX Florence is said to have had zero successful attempts since opening nearly three decades ago.
The facility is known to be 'the only prison specifically designed to keep every occupant in near-total solitary confinement', as per Corrections1.
Not only do the inmates have limited contact with fellow prisoners but, according to El Chapo, he's been left unable to have phone calls or visitors.
In a letter to District Court Judge Brian M. Cogan in the Eastern District of New York last year, he claimed that 'the facility stopped giving me calls with my daughters. And I haven’t had calls with them for seven months'.
Advert
Implying that it was only him to be subjected to such strict measures, El Chapo labeled it as 'unprecedented discrimination against [him]', AP News reported.
Niamh Shackleton