Campaigners opposing the M3 motorway's routing near the Hill of Tara will today protest outside the Department of the Environment.
The demonstration will call on the new Minister for the Environment, the Green Party's John Gormley, to reverse the decision of former minister Dick Roche and re-route the road.
Campaigners say their case against the routing has been strengthened following the discovery of new archaeological sites in the area on Saturday.
A stone underground chamber and an underground stone passageway with wooden entrances — apparently linked to a complex of underground souterrains — must be saved, Tarawatch spokesman Vincent Salafia said.
A handful demonstrators gathered outside the Custom House in Dublin at midday. Later today they will present a submission to Mr Gormley stating that the National Monuments Act requires him to halt works following the latest archaeological find, while the National Museum is consulted.
But the National Roads Authority maintains the sites are not a unique feature and it had been aware of the site for months.
While it is the Minister's function to declare a site a National Monument, the roading authority has said it did not believe this weekend's discovery warranted such a classification.
Mr Gormley said last week that he could not overturn judicial decisions already made in relation to the national monument at Lismullin, Co Meath and the approval of the M3 route.
After reviewing Lismullin files last week, he said, Mr Roche had done what was legally required for approval as he had consulted with the National Museum and its chief archaeologist.
Mr Gormley said he planned to meet with archaeological experts and the National Museum director this week.