Tara was the seat of the High Kings of Ireland, dating back to 2000 BC, see http://www.yourirish.com/history/ancient/high-kings/. It is hard to fix where myth ends and historical figures begin, however, but their powers were broad-based and provided for annual gatherings, public works, collection of taxes, providing for defense and emergency, and legal judgments and setting laws.
Standing stones: a famous one is at Tara. See others at Standing-stones-jhwh-flip-flopper.html, an overview of Biblical, other ancient, and modern, standing stones.
But it also is one of the most frustrating because the Christian world coopted on (piggybacked) ancient ways, the Christians tried to Christianize the old religious, royal and civic sites, to the diminution of both ideas. It is hard to get a photo of the main event without also a cross or other Christian thing entering in. On the cut-off side here of our photo of the primary standing stone, this obvious phallus-obelisk form so common in the world (Washington Monument anyone?), is a cross.
- The Five Roads to Tara. In the times of the ancient kings, apparently there were five roads from each of the kingdoms to Tara, one of which was the major east-west route from Galway to Dublin, near Tara. That may be becoming a "monastic route" for tourists, and we hope the other routes also can help organize trips to Ireland, see http://www.tarataratara.net/resources/Tara_roads/Tara_Five_roads.htm