A "deserted village" dating back to pre-Famine times on the slopes of Slievemore, the highest mountain on Achill Island, Co Mayo, is under threat from the large numbers of tourists who visit the site every year.
Ms Erica Hanning, one of the archaeological supervisors on the site where 74 roofless buildings out of a total of 137 standing in the 1830s remain, warned at the weekend that tourists poking about in standing walls looking for nice stones as souvenirs are causing problems.
"They pull out stones here and there and eventually a whole wall tumbles," said Ms Hanning, an American who is attached for a second year to the Achill Archaeological Field School.
"These people seem to forget they also have a duty to conserve the past. I would say to them, you are destroying your own past. It is better to leave it for future generations."
Ms Hanning also highlighted the damage done by treasure hunters with metal detectors on the site.
"There is really nothing for those with metal detectors to find here," she said.
"The people who lived in this village over the centuries were very poor. The most that is ever found is a horseshoe or part of an old farm implement. The treasure hunters end up disappointed and we end up with a very large hole in the ground."
Ms Hanning said in recent times senior archaeologists had to march visitors off the site because they wanted to take stones with them as souvenirs.
She reminded treasure hunters that a fine of up to €50,000, plus a year in prison, can be imposed on anybody who takes a metal detector onto an archaeological site in Ireland.