A protest march on Saturday against the planned route of the M3 motorway - billed as a "last call to save Tara" - is taking place amid indications that the setting of Ireland's ancient royal site is coming under development pressure.
Opponents of the controversial scheme have also claimed that at least two sites that would warrant designation as national monuments have been found during archaeological excavations along the route of the motorway.
The "Save Tara Valley Awareness March" is being held against the backdrop of litigant Vincent Salafia's decision to withdraw his appeal against a High Court decision dismissing his case against the chosen route of the M3.
Plans by JMP Construction Ltd to build a recycling facility adjacent to the planned M3/N3 interchange at Blundelstown are being opposed by conservationists on the basis that it would be located within sight of the Hill of Tara.
Dr Muireann Ní Bhrolcháin, lecturer in Celtic Studies at NUI Maynooth, said the proposed recycling facility would "permanently degrade the archaeological landscape" of the Gabhra valley, between the hills of Tara and Skryne.
In her letter of objection to Meath County Council, she said the valley was recognised as "an area of high archaeological importance . . . part of the extended landscape of Tara". It "should be treated with the greatest care".
Dr Ní Bhrolcháin said the proposed development "directly contradicts" an assurance given by Minister for the Environment Dick Roche that heritage protection would take priority over development at the Blundelstown interchange.
Giving his approval for archaeological excavations along the M3 route in May 2005, Mr Roche said the aim would be "to protect the rural character, setting and archaeological heritage of the landscape" in the vicinity of Tara and the new motorway.
"If this application is permitted, it will breach the instructions given by the Minister," Dr Ní Bhrolcháin said.
The aim of the march on Saturday, starting at 2pm from Railway Street, Navan, is to "create awareness throughout Ireland and internationally that the Tara Valley will be needlessly destroyed by the proposed M3", according to the organisers.
The Save Tara-Skryne Valley Campaign has the full support of former arts and heritage minister Michael D Higgins TD (Labour), who described Mr Roche's approval for the M3 as "an appalling decision which will affect . . . generations to come".