Inside the new $300 million Auckland Prison with a sensory garden

A $300 million dollar prison for the country's most dangerous men has been opened on the Auckland Prison grounds at Paremoremo.

The new facility has a purpose-built mental health unit designed for the most acutely unwell prisoners, and a sensory garden - a first in New Zealand prisons.

Corrections CEO Ray Smith says: "The prisoner we deal with today is a much more hardened prisoner than we dealt with 20 to 30 years ago. Many people don't respect authority, they don't even respect themselves."

That means secure covered walkways and security tailored to different risk levels.

This is a dry cell with no toilet, where prisoners concealing drugs inside their bodies will be held here until they use a bathroom.

The entire facility is a single story because escorting prisoners on stairs is highly dangerous, and there's more space for officers to regain control of a situation.

"It's very hard in the old facility, there's a lot of moving of people around, you can't even shower in your own cell which means you're always moving people who are volatile and unsettled," Mr Smith said.

The new cells are roughly 30 percent bigger than the old ones, and unlike the old facility they have their own shower, their own toilet and their own window, through which prisoners get a glimpse of green.

Howard Justice League member Mike Williams said: "There's light, you can stand on the grass, you can stand in the sun, you can do none of those things at the old facility."

What's also changed in 50 years is inmates' mental health, 90 percent have a lifetime diagnosis of mental health or substance abuse issues. 

The new prison has 68 mental health beds and a sensory garden to provide a place of calm, there are plants with different textures and smells like thyme and spearmint.

There are also exercise yards and facilities to teach inmates new skills

All are measures Corrections hope will give the men who end up behind the wire some chance of rebuilding their life.