But this fortress was built to keep people in, not out.
The 200-year-old high-security prison is the new home of Daniel Kinahan, leader of the Kinahan Cartel – one of the world's most powerful crime gangs.
Extradited from Dubai on Sunday, the 49-year-old is awaiting trial on charges of directing a £1billion criminal organisation with drug smuggling, gun running and money laundering operations spanning five continents.
Confined to his cell for 20 hours a day, Kinahan will have plenty of time to contemplate the dramatic change in his fortunes.
Gone is the five-star luxury of Dubai's £1,000-a-night Burj Al Arab hotel, where he wed fellow Dubliner Caoimhe Robinson in 2017. Today, his only creature comforts come courtesy of the prison tuck shop.
And while he once enjoyed the company of elite athletes like Tyson Fury, Kinahan now finds himself living alongside some of Ireland's most dangerous criminals, from multiple murderers and rapists to paramilitary enforcers.
Located on the edge of the county town that gave the jail its name, Portlaoise formerly housed IRA inmates who were guarded by Irish Army troops patrolling with anti-aircraft machine guns.
Portlaoise Prison is the new home of Daniel Kinahan, alleged leader of the Kinahan Cartel, one of the world's most powerful crime gangs.
Kinahan, sat in the back of the car, leaves the Criminal Courts of Justice in Dublin on Sunday
Kinahan was taken from court to the prison in a bomb and bullet proof van
Its years as a paramilitary lock-up were marked by several high-profile incidents, including the daylight escape of 19 republican prisoners who overpowered guards and used explosives to blast their way through interior and exterior walls.
In the same year, 1974, Provisional IRA prisoners held 27 guards hostage for six hours, forcing the Army to storm the jail to regain control.
Kinahan has been moved onto A Block, a 'prison within a prison' reserved for the most high-risk inmates.
He is believed to be sharing a landing with 44-year-old crystal meth smuggler Nathan McDonnell and triple murderer Andy Cash, who stabbed his younger brother and two sisters to death in 2022.
Among his other neighbours are father-and-son duo Kenneth and Dean Fitzsimons, who last year beat, burned, stabbed and branded a man with the word 'RAT'. Unlike most prisoners on the high-security wing, the pair share a cell.
Elsewhere in the facility are Benjamin Morrissey, a notoriously volatile inmate who was transferred to Portlaoise after slashing a prison officer across the face at another jail, and cop-killer Aaron Brady, who once stabbed a rival 16 times before setting him on fire during a prison brawl.
Kinahan will spend the bulk of the day in his cell and speak only to prison officers, who will deliver breakfast at 8am, lunch at 12.30pm and dinner at 4.30pm. His diet will be bland and repetitive: cereal for breakfast and 'meat and two veg' for lunch rounded off by a dinner of sausages and baked beans.
It is understood prison guards will work on rotation as a security precaution to minimise the risk of cartel associates targeting staff or their families.
Kinahan will exercise alone in the yard, which is covered with wire netting to prevent contraband being dropped in by drones, while a glass pane will separate him from in-person visitors, such as members of his legal team.
Chris Dalby, director of consultancy World of Crime, told Irish media there was a 'very credible fear' Kinahan could be assassinated by a gangland rival or a former business partner worried he might pass on information to the authorities.
He also warned of a potential rescue attempt by elements of the Kinahan Cartel who remain at large.
The Irish authorities are taking no chances, escorting him to court in Dublin in a bomb and bullet-proof van and sweeping court buildings for explosives.
Kinahan's fellow inmates include cop-killer Aaron Brady, who once stabbed a rival 16 times before setting him on fire during a prison brawl
The cartel boss is believed to be sharing a landing with 44-year-old crystal meth smuggler Nathan McDonnell
Among his other neighbours is Kenneth Fitzsimons, who last year beat, burned, stabbed and branded a man with the word 'RAT'
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Kinahan has himself voiced fears that he could be targeted, telling podcaster James English: 'If I happen to fall and bang my head when I have handcuffs on me, I didn't fall. If I end up hanging myself, killing myself, poisoning myself, it didn't happen. I'm not suicidal.'
He will be safe in his solitary cell on A Block, where he will be kept on suicide watch and monitored 24 hours a day.
A business leader with ties to a member of the Kinahan Cartel played down fears he could be targeted elsewhere in the prison system, including by affiliates of the group's deadly enemy, the Hutch crime family.
'The cartel basically control much of the prison system in Ireland so any threat to Daniel when he comes off segregation will be negligible,' he told the Daily Mail.
'I do know the cartel are not worried in the slightest about anything the Hutch camp might be thinking about. They are seen as done now.'
Another senior Kinahan Cartel member, Sean McGovern, is also being held on the A Block, but it is unlikely they will be allowed time together.
McGovern, who was extradited from Dubai in May, was jailed the following month for 24 years after he pleaded guilty at the Special Criminal Court to two charges of directing a criminal organisation.
One charge was linked to the murder of Noel 'Dick Egg' Kirwan, who was shot dead in Clondalkin in December 2016, and the other to a foiled plot to kill James 'Mago' Gately.
During his time on remand, Kinahan – who has said he expects to receive a life sentence – will be housed within the A5 unit of the ultra-high security block.
Conditions will be a marked improvement from the 'hellish' Al Awir Central Jail in Dubai, with the mobster controversially given access to his own gym with free weights and a treadmill. He will also have a TV in his cell and enjoy access to his own private library.
Members of the Irish military stand guard at Casement Aerodrome, where Kinahan arrived on a flight from Dubai
Portlaoise Prison was previously reserved for violent republicans, but now holds a more mixed population
Even so, he is unlikely to find much reason for cheer. In 2019, an internal report by Portlaoise's chaplain said the segregation on A Block made 'interaction of any reasonable kind almost impossible'.
There are no workshops attached to the block, while there is only limited access to educational activities. Families can only visit prisoners through a screen, although Kinahan will be able to video call his family in Dubai.
The gangster appeared on Sunday at the Special Criminal Court wearing a black hoodie, black tracksuit bottoms and white trainers, with observers describing him as looking pale and older than in recent photographs.
When it was explained to him that he could file an application for bail through the High Court, he replied: 'I think we all know I won't be getting bail, but thank you for your time.'
Kinahan appeared without legal representation, although his lawyers have previously insisted the allegations that he is a crime boss are false and unsupported by evidence.
With his next court hearing set for October 5, he has plenty of time to settle into his new life.