A grouping of ancient earthworks that covers nearly two square miles, this ancient site includes ring forts and a large mound that may actually be a passage tomb similar to the Mound of the Hostages at Tara in County Meath. There are a number of enclosures that also appear to be tombs. One is said to be that of King Dathi, the last of the pagan kings of Ireland. It is marked by a standing stone nearly seven feet tall. Megalithic tombs of several varieties are common to this area as well.
History describes the Rathcrogan and Glenballythomas site as possibly the place used by the Kings of Connaught for coronations and traditional feasts.