It is the home of Australia's most notorious criminals, like Ivan Milat and Bassam Hamzy — and it is not exactly known as a pleasant place to be.

Prisoners at Goulburn's Supermax spend the majority of their days in their cells, are constantly monitored and often only have contact with one other inmate.

But a $47-million makeover will see the complex broken into two separate wings and it is hoped one will act as a "half way" between Supermax and a regular prison, where eligible inmates can be rehabilitated and eventually moved to lower security settings, said Corrective Services' Assistant Commissioner of Custodial Corrections Kevin Corcoran.

Mr Corcoran said the new wing would still have a number of restrictions, but eligible inmates would be able to socialise more than they do currently and enter education programs.

"We're looking at making sure that we have appropriate step down facilities available to us, which we don't have at the moment, so that we bring people through, hopefully disengage them from their extremist views and move them out into the mainstream prison population," he said.

Mr Corcoran said the decision of who makes it there was made by an "extreme threat-management committee", which analysed inmates' behaviours.

A single cell in the new Goulburn Supermax wing. ( Supplied: Corrective Services NSW )

The number of beds was also increasing from 56 to 102 in line with projections about how many inmates would have to be placed in the Goulburn jail, Mr Corcoran said.

"We're looking at not only terrorists, but outlawed motorcycle gangs and organised criminals, so we have that capacity in the future," he said.

A double cell in the new Supermax. ( Supplied: Corrective Services NSW )

Changing extremist views

Dr Clarke Jones, a criminologist with Australian National University who has studied prison radicalisation, said high security settings generally were not "conducive to change amongst offenders".

"When we're looking at the vast majority of terrorist offenders, who have been incarcerated because of new laws that have been created — they've been planning or amassing materials — [they'd] probably be better in a mainstream facility where they have opportunities to engage more broadly in prison programs, mix with other types of offenders, that's going to create a better chance for change," he said.

"If they're sitting idle and they're isolated either on their own or with another offender and are only allowed out very few hours in the day, it's very hard to ask someone to change."

But, he said, that did not apply to inmates who were a threat to themselves or other prisoners.

Greg Barton, a research professor in Global Islamic Politics at Deakin University, said efforts to de-radicalise prisoners with extremist views had variable results, "but it would be negligent not to try".

"It's very hard to quickly and reliably de-radicalise someone," he said.

He compared it to drug and alcohol rehabilitation programs where, he said, it worked for some and not others, but the success cases validated the cost.

"We say prisons should be part of rehabilitation and the argument for attempting to do this, instead of not trying, is considerable."