International academics will gather at the Hill of Tara site on Sunday to protest against the M3 motorway planned for the area.
Last month, Minister for the Environment Dick Roche cleared the way for the construction of the controversial project by issuing instructions to Meath County Council on how archaeological work is to be carried out.
The international scholars - who are experts in Celtic studies, Irish history, Irish literature, linguistics, archaeology and anthropology - sent a petition to the Irish Government in April calling on it to re-route the motorway through the Tara/Skryne Valley.
The academics are based in various European countries, the United States and Canada, Australia and Russia.
The project was approved by An Bord Pleanála two years ago, but many archaeologists and historians have argued that part of Ireland's most important heritage site will be destroyed.
Dr Edel Bhreathnach, medieval historian at UCD, told ireland.comthe experts from around the world will gather on Sunday to emphasise the same message as campaigners here: "This is a group of people who cannot be accused of being narrow-minded or not open to argument, as campaigners have been referred to.
"They know exactly the scale of the tragic loss that will be caused by the M3 through Tara and Skyrne Valley," she added.
The academics will also be attending the Ulster Literary Cycle lecture series at Maynooth University.
They will be discussing ancient mythical tales such as Irish epic Táin Bó Cuailnge (The Cattle Raid of Cooley), which claims warrior Cu Chulainn's head and right hand are buried at Tara.
Some visitors marking summer solstice celebrations at the Hill of Tara this week also held a silent protest at the motorway plans.
Those attending at Tara on Sunday include Henry L Shattuck, Professor of Irish studies at Harvard University; Professor Joseph F Nagy, Department of English, University of California, Los Angeles; Professor Ronald Hicks, professor of anthropology, Ball University, Indiana; Professor Ann Dooley, University of Toronto; and Dr Charles Doherty, School of History, University College Dublin.