The "poster child" of Britain's super prisons is opening in Wrexham. But how will HMP Berwyn compare to other jails?
It cost £250m to build and has a capacity of 2,106 prisoners - 500 more than the biggest current prison in England and Wales was built to hold.
And HMP Berwyn in Wrexham is welcoming its first inmates on Tuesday.
The prison service has come under increasing pressure in recent years due to overcrowding, with 6,000 assaults on staff and 105 suicides up to June 2016.
The UK government has pledged to spend £1.3bn on new prisons, and after the riots in HMP Birmingham last year, Justice Secretary Liz Truss said the new Welsh prison "will help to reduce overcrowding across the estate".
HMP Berwyn is the government's first publicly-run super-prison - holding more than 2,000 inmates. Nine more new prisons are expected to open by 2020.
Andrew Neilsen, from the Howard League for Penal Reform, said: "Berwyn has become a bit of a poster child for super-prisons. It is the first public sector prison to be opened in England and Wales since the 1990s, and they want to show it can work.
"Russell Trent, the governor, is seen as a high-flying trouble-shooter. He has turned around failing institutions in the past. He has been tasked with setting up an institution and getting it off on the right foot."
But just how much difference will HMP Berwyn make, and does it herald a new era for prisons in England and Wales?
1.It will be the biggest prison in the UK - just
When the building of HMP Berwyn was started it was set to provide 500 more places than the current biggest prison in England and Wales - privately run HMP Oakwood in Staffordshire.
Privately-run Oakwood, managed by security company G4S, had 1,600 places when it opened in 2012.
However, due to overcrowding in prisons across the UK, Oakwood further increased its capacity last year by converting some single cells into rooms which could hold two inmates and can now hold up to 2,096 prisoners.
2.Will Berwyn make a difference to overcrowding?
The vast majority of prisoners in England an Wales are housed in what the Ministry of Justice define as a "good, decent standard of accommodation" - known as "certified normal accommodation" or CNA.
An additional 6,512 prisoners are currently incarcerated over that number.
While the 2,106 new prison places provided by HMP Berwyn will help address this, they will not all be instantly available as HMP Berwyn will not function at capacity for some time.
3.Cheapest prison in England and Wales
The new super prison is anticipated to be the cheapest to run per prisoner in England and Wales.
It is expected to run at £14,000 per head per year, including overheads.
The second cheapest prison will be the second biggest - HMP Oakwood - at £19,505 per head.
4. It is dwarfed by the biggest prison in the USA
America's LA County jail is almost 10 times bigger than HMP Berwyn with around 17,000 inmates, although it is not strictly comparable as it is made up of a collection of facilities spread over a wide area.
The United States does have the highest incarceration rates in the world with figures for 2014 showing 690 prisoners for every 100,000 people, compared to 146 in England and Wales.
England and Wales had the highest incarceration rate in Western Europe, according to Eurostat figures for 2014.
The prison population in the UK has almost doubled since 1993 over a period when the overall population of England and Wales has grown by about 17%.
- Additional reporting by Gwyndaf Hughes