Plans to build a motorway close to one of Ireland's most historic sites have been attacked by campaigners as "a crime against humanity".
The road will be close to the ancient monument
The Hill of Tara and its ancient burial site in County Meath is Ireland's equivalent of the Valley of the Dead in Egypt, campaigners have said.
Environmentalists and historians have called for the proposed M3 motorway to be stopped.
The proposed route will take the motorway through the Tara-Skryne
The road will be largely along the current Enniskillen to Dublin road, north-west of the capital.
Tara, known as Temair in Gaeilge, was once the ancient seat of power in Ireland - 142 kings are said to have reigned there in prehistoric and historic times.
In ancient Irish religion and mythology Temair was the sacred place of dwelling for the gods, and was the entrance to the otherworld.
Dr Muireann Ni Bhrolchain, lecturer in Celtic Studies at the National University of Ireland Maynooth, said that Tara was a monument of massive importance.
She said: "The historical significance of Tara is that it is 6,000 years old.
The mound of hostages is the oldest monument on the Hill of Tara
"It has been inhabited by the kings of Ireland, as far as we know, and by the most important inhabitants of Ireland for that period of time.
"The king of Tara would have been considered the most important king of Ireland up until the 11th or 12th century."
Archaeologists say the nine-mile stretch of motorway will mean the excavation of at least 28 sites and monuments in the road's corridor.
They expect many more sites will be affected, with 48 archaeological zones within 500 metres of the road corridor and about one site every 300 metres along the road itself.
Vincent Salafia from Save the Tara-Skryne Valley campaign has vowed to make a legal challenge against the motorway.
He said: "This is a crime against humanity.
"The Hill of Tara is our most important national monument. Even the name worldwide evokes the spirit and soul of Ireland.
"It is not just the motorway we are objecting to. Everything that comes with the motorway will turn this area into an industrial area."
The planning appeals board (An Bord Pleanála) took archaeological objections into account when it gave its permission for the project
The National Roads Authority said the motorway was needed because it can currently take up to two hours to travel the 25 miles between Navan and Dublin.
Michael Egan from the NRA said that the road would be twice as far from the hill as the current Dublin to Navan road.
He said it would be 1.5 miles from the top of the hill to the motorway.
"The board gave its approval to proceed with the construction of the road on the basis that it concluded that the road would not have significant environmental effect and would not impact on the hill of Tara," he said.
Work on the motorway is due to start in 2005 and finish three years later.