8Newman, Conor. Tara: An Archaeological Survey. Dublin: Royal Irish Academy for the Discovery Programme, 1997, pp. 225-230.

According to the author, "The earliest identifiable monument is a postulated palisaded (?) enclosure of Neolithic date, part of which was uncovered in pre-tomb levels during excavation of Duma na nGiall [the Mound of the Hostages] and radiocarbon-dated to 3030-2190 BC."

Today one can see 25 monuments on the Hill of Tara. Twice that number have been discovered by geophysical means and through aerial photography. (Bhreathnach, Edel, and Conor Newman. Tara, Co. Meath: a Guide to the Ceremonial Complex. Archaeology Ireland, 2008, pp. 1-6.)