Conservationists have urged visitors to the Howff cemetery not to sit on the historic gravestones for fear they could be irreparably damaged.
The warning comes after a man was pictured sitting on an ancient headstone with a dog close by.
The witness who took the picture said he thought it was “disrespectful” to rest against the stones.
He said: “I saw the guy sitting down and couldn’t believe he was sitting on the headstone in the shade.
“I know these graves aren’t visited by family members but I still found it incredibly disrespectful.
“The dog owner was sitting there checking his phone, from what I could see.
“I’m not sure if the guy was doing anything wrong. It wouldn’t be acceptable in any other cemetery so why should this be any different?”
Simon Goulding, Dundee’s Howff Conservation Group chairman, said the group would be putting up posters to remind people not to sit – or even sunbathe – on the gravestones.
He said: “Incidents such as this are uncommon, but there were reports of someone sunbathing on one of them in the past.
“We’ve previously had posters inside the Howff urging people not to sit on them as they extremely fragile. There are plenty of benches within the grounds to enjoy the Howff.
“These stones are decaying at a fast rate and people sitting on them will not be helping the situation.
“We will be putting more posters up, just to remind people of their conduct in the Howff.”
There are an more than 60,000 recorded burials at the Howff, although the conservation group believes there could be as many as 80,000.
Last week police were called to the cemetery following reports that a woman had been seen “injecting” drugs into her groin, although officers later confirmed no offences were detected.