Excavation work at the national monument found in the path of the M3 motorway has begun.
Archaeologists began preliminary work on the site this morning after protestors who had blocked their way were moved aside.
The stand-off began on the road leading to the Lismullen site at around 7.30am. A group of around 20 protestors linked arms and refused to let vehicles pass onto the site.
Gardaí from Navan were called and after a discussion, the protestors stood aside and let the vehicles and the archaeologists pass.
Protestors maintained a vigil at the scene for around three hours before dispersing.
Protestors claim the excavation of the site and its 'preservation by record' amounts to destruction, which they say is illegal under EU law. The Department of the Environment disputes the claim.
The site at Lismullen consists of the remains of two large circular enclosures. It was originally made from wood but that has since rotted away leaving visible marks in the soil.