Archaeologists have learned that the national monument discovered during works on the M3 motorway at Lismullin, Co Meath is more than 2,000 years old.
A number of stake holes that would have formed an enclosure were discovered by archaeologists working on the controversial site and radio carbon dating has indicated they have been there since the Iron Age.
"Right now we are interpreting the site as being an open air ceremonial enclosure. Once we begin excavating we will know a lot more," said Mary Deevy, project archaeologist with the National Roads Authority.
The recent spell of bad weather has delayed the archaeologists' progress at Lismullin but contractors Eurolink remain confident that the works will be carried out appropriately and on time.
"The next step will be a geophysical survey of the enclosure once the weather improves. As soon as that is carried out we can begin excavating the enclosure," Ms Deevy said.
An underground souterrain from about the 10th century has also been discovered on the site. Archaeologists said it was possibly used for defence during the Viking invasion.
Once the excavation is complete the building of the motorway will commence and the monument will be preserved only by record.
Protesters against the M3 development continue to gather at the Lismullin site.
Earlier this week there were heated exchanges between protesters, construction workers and security personnel. The exchanges resulted in seven arrests.
