Magh Adhair - "Adair's plain" - sits near the village of Quin in County Clare, in what was once the heartland of the kingdom of Thomond. The site has not been excavated, so its earliest date is speculation. The mound is likely to have been built sometime between the Bronze Age and the Iron Age, given the form of its surrounding monuments. What is certain is that it remained in use - in some form, across phases - for at least fifteen hundred years. The 19th-century antiquarians John O'Donovan and T.J. Westropp argued that the name "Magh Adhair" once signified the entire plain of Clare itself, with the great central feature - the inauguration mound - giving its name to the whole region. Over centuries the name shrank until it referred only to the field where the mound stands.

The central monument is a low, ovular mound surrounded by a fosse, with a bridging point on the west side leading to a flat platform on top. A smaller satellite cairn sits to the west. North of the main mound is a bullaun stone - a flat block carrying two carved depressions that fill with rainwater. North and west of that is a series of enclosures and the recorded site of a battle in 877 AD. Bordering the entire complex on the west is a small river named, in English, the Hell river; beyond it stands a single standing stone, called a ligaun. The whole assemblage sits in a natural amphitheatre of low hills. Floods come through here regularly. East of the mound is a turlough - one of the seasonally vanishing lakes peculiar to Irish karst landscapes - and a fulacht fiadh, an ancient cooking pit.

From around 100 AD - the suggested date for the Gaelic Milesian colonisation of Clare - until the medieval period, Magh Adhair was the inauguration site of the Kings of Thomond, the North Munster polity of the Dál gCais. The most famous of those kings was Brian Boru, whose dynasty - the O'Briens - dominated medieval Munster and produced the High Kings of Ireland in the early 11th century. The Caithreim Thoirdhealbhaigh, a medieval account of the Anglo-Norman wars in Thomond, records inaugurations at Magh Adhair in 1242, 1267, 1277, and 1311. The 1311 ceremony for Dermot O'Brien, candidate of Clan Brian against the Anglo-Norman de Clares, ran like this: his chiefs gathered around him at Moy Eyre (an older form of the name), and a man named Loghlin son of Cumee performed the installation. A bard recited the inauguration poem - declaring him "the valorous griffin... heart of the territories, a tree under blossom" - and the assembled tribes consented.

The pre-Christian mythology attached to the mound runs deeper still. According to Frost's History and Topography of the County of Clare and the 1839 Ordnance Survey letters of O'Donovan and O'Curry, Magh Adhair was named for a chieftain of the Fir Bolg called Adhair (or Aed), the son of Umor. He was the brother of Aengus, the same legendary builder credited with constructing the cliff fort of Dún Aengus on Inishmore. In the medieval mythological cycles - the Book of Invasions and related texts - the Fir Bolg were driven into Connacht after their defeat by the Tuatha Dé Danann. Clare, being west of the Shannon, was part of that displacement zone. Whether any of this corresponds to historical migration or is purely literary invention is impossible to know. What survives is the persistence of the name: every retelling came back to the mound and the chieftain it remembered.

Inauguration ceremonies at Magh Adhair ended during the Anglo-Norman wars and the gradual collapse of Gaelic political institutions in the late medieval period. But fair gatherings - irachts - continued at the site for centuries after, as late as the 19th century. The last documented fair at Magh Adhair was held in 1838, though there are hints that informal gatherings continued until the Great Famine emptied the surrounding parishes a decade later. The site, technically in the territory of the O'Hehir clan before the MacNamaras displaced them, became overgrown. The mound is now degraded by cattle, the fosse partly filled in. The local English-language nickname for the place became "Cregnakeeroge" - a Ciaróg being an Irish word for an insect, specifically a beetle - a name that does no justice at all to a place that consecrated kings for a millennium and a half.