Early morning joggers, walkers and cyclists have woken on Friday to find Wollongong's two lighthouse along The Blue Mile have been defaced.
Climate Justice Now has been written in red paint on both lighthouses.
It happened overnight just hours before rallies are planned to be held in Wollongong and 100 other locations around the nation calling for climate justice.
Wollongong Lord Mayor Gordon Bradbery said there were better ways to get the message across than defacing such iconic heritage listed structures in the city.
"I can understand people's passions and concerns about climate change and the issues that confront us but to put graffiti on the lighthouse was not exactly a smart move," he said.
"It might have brought attention to their cause but at the same time it has brought a negative response.
"I fully appreciate the passion of the people involved but at the same time council and the community are worried about graffiti of that nature especially on an asset like that".
Cr Bradbery said council crews were quick to clean much of the red paint off the two lighthouses on Friday morning.
On Monday council will paint over what is left with white paint.
Benjamin Gava found the graffiti on his early morning jog.
"I was quite surprised to see it at first, but the more I thought about it the more I felt "good on them, whoever it was." I think most people understand that we are facing a climate emergency and that more needs to be done to limit climate change and its detrimental impacts," he said.
"Unfortunately we seem to be living under a system that demands infinite growth of a finite world and rewards greed above all else, a system ever more self serving and increasingly detached from the wants and the needs of ordinary people and the limits of the natural environment.
"I guess when those that are meant to be leading us fail to hear the pleads of the people, the people will resort to increasingly desperate measures to be heard".
Other onlookers were not so sympathetic and were horrified that anyone would do that to two such important landmarks.
Lighthouses of Australia president Ian Clifford is involved in the maintenance of both heritage listed lighthouses and said he recognised the cause and what was trying to be highlight on Friday.
But Mr Clifford was surprised if anyone who genuinely believes in the cause would go to such lengths.
"It is not a great way to highlight the cause," he said.
Mr Clifford informed the organisations responsible for looking after the two lighthouses to inform them of the mess made overnight. He said NSW Police were also being informed.
Mr Clifford said graffiti on the two lighthouses was fairly rare.
"Nationally we don't have much of a graffiti issue with the lighthouses," he said.
"From time to time we get a little bit of it in Wollongong. It often occurs on a Thursday night".
Mr Clifford said Lighthouses of Australia activate the Breakwater Lighthouse, which is not an active lighthouse, once a year to demonstrate its operation.
That occurs on the mid weekend in August. It is turned on for four nights from Thursday to Sunday.