Megalithic simply means built of large stones, and in an Irish context the term covers a broad family of monuments, from portal tombs and passage tombs to court cairns and dolmens, most of them dating to the Neolithic period, roughly four to six thousand years ago. Mayo has no shortage of such monuments, the county's boglands and upland pastures having preserved, beneath peat and scrub, traces of a prehistoric population whose building ambitions were considerable. What sets Cloonconlan apart, at least for now, is a particular kind of obscurity: the structure is recorded and classified, it holds an official place in the national inventory of monuments, and yet almost nothing about it has been made publicly available.