A peace park was unveiled at Tighes Hill on Sunday to honour past and present activists and "encourage future ones", amid concern about nuclear war.
The Hunter Peace Group had been advocating for the park for years.
The group's secretary Lynda Forbes said the "City of Newcastle's Peace Park" was aimed at "encouraging people to continue to fight for peace and Newcastle to be anti-nuclear".
The park's opening at a reserve in Maitland Road followed the risk of nuclear war hitting its highest level since 1947, with the Doomsday Clock moved in January to "90 seconds to midnight".
The opening was held on Hiroshima Day, which commemorates those killed in World War II by two US-detonated atomic bombs in the Japanese cities of Hiroshima and Nagasaki.
The federal government plans to acquire nuclear-powered submarines, worth up to $368 billion, under the AUKUS partnership. Newcastle is being considered as a base, along with Port Kembla and Brisbane.
Hunter Workers secretary Leigh Shears said Newcastle was made a "nuclear free zone in 1982", with the backing of the city council and union movement.
Mr Shears said it should be highlighted that war involves "working class kids sent abroad to kill working class kids".
"They're sent to fight the wars of the bosses and governments," he said.
He said "nations need to be prepared to defend themselves", but the previous and present federal governments were "looking to be seen as more hostile than in previous years".
Lord Mayor Nuatali Nelmes and Mrs Forbes unveiled the plaque for the peace park.
Cr Nelmes said the park was "a commitment to the values it represents - peace, unity, and understanding".
"This park shall serve as a symbol of our shared responsibility to create a peaceful world," she said.
Federal Newcastle MP Sharon Claydon spoke about the effects of atomic testing on the Anangu lands at Maralinga.
"Those tests across those lands and the 1800 Aboriginal people whose lives were profoundly changed are a very strong reminder of why a voice is so important," she said.
"For too long the voices of Aboriginal people to government have been too easily dismissed."
Ms Claydon said she had "no doubt Newcastle will send a yes vote in the referendum".
She urged people to do everything they could for the Voice "in the spirit of peace and continued activism for social justice for our nation".
