After months of work the group created mosaics, paintings, tuku tuku panels, stone carvings, a karaka tree and wind chimes.
At the unveiling one man spoke about the significance of the karaka tree.
"Like the fruit of the karaka tree, Karaka Unit offers fruit in abundance to feed the hearts and minds of those who have come to seek a new direction for their lives."
He said the Karaka Unit is an opportunity for men to make timely decisions that could change the course of their life.
Another man said the project was fun, therapeutic and rewarding.
The Special Treatment Unit provides treatment programmes for high-risk violent offenders and medium to high-risk adult sexual offenders.
The programmes are designed to help the men gain insight into their unhelpful behaviour patterns and develop ways of coping with life stress.
They assist the men to make positive changes in their lives with the aim to avoid future offending.
Director Ann Byford says working with a group of men at various stages of treatment was a rewarding challenge.
"What it takes is patience, humour and passion."