Pictures taken at the tunnel, which connects the northern and southern sections of Glebelands Park, show some of the artwork that has already taken shape – including a snarling tiger.
A statement from Newport City Council said they wanted the space to “encourage creativity in a safe environment” while reducing the presence of graffiti in unauthorised areas.
A sign in the tunnel says the wall is a “canvas” where artists can bring their ideas to life and sets out ten rules, including a ban on tagging and offensive imagery or language.
The space has been allocated with the blessing of Newport council, St Julians councillors, Welsh Government and the South Wales Trunk Road Agent, which manages 900km of highway from Pembrokeshire to the Severn Crossings.
St Julians resident Curtis Jones, 28, says he was involved in the council’s consultation process about how legal graffiti spaces have worked in other areas.
“It’s going to brighten up a neglected area, give somewhere for people to express themselves and save money painting it all grey every few weeks, too,” he said.
“The space will showcase some incredible talent from local artists and allow a space for beginners to practise and be inspired.”
Council leader Jane Mudd and cabinet member for climate change and diversity Cllr Yvonne Forsey joined St Julians councillors Phil Hourihane and Paul Bright at the unveiling.
Cllr Forsey said: “I’m delighted that we have been able to dedicate this wall as a legal graffiti space.
“We are committed to improving our city’s physical environment, and we also recognise the need to give young street artists a safe area to work in. We really hope that the wall can become a valued creative outlet for our local community.”
This project follows the commissioning of a number of murals across Newport as the council aims to improve the city’s physical environment.