It is a rath, the Irish term for a ringfort, the type of enclosed farmstead that was built in its thousands across Ireland during the early medieval period, roughly between the fifth and twelfth centuries. Most were the homes of farming families, defined by a circular bank and ditch that marked territory as much as they provided defence. This one at Glengoole is modest but legible once you know what you are looking for.

The structure takes the form of a raised circular platform with an internal diameter of around 21 metres north to south, and an overall diameter of roughly 27 metres north to south and 24 metres east to west. It is defined by an earth and stone bank that survives in places to an external height of between 0.8 and 1.5 metres, with a base width of 5 metres. A second ringfort of the same type lies approximately 300 metres to the north-east, suggesting this was once a more populated corner of the landscape than it appears today. The Glengoole example has not survived intact. A roadway has cut through the enclosing bank from the north-east around through the east and down to the south, reducing that section to little more than a scarp. The bank is best preserved along the arc running from the south, through the west, and up to the north-west, where the original profile remains clearest and the slight but distinct curve of the earthwork reads as a deliberate human construction rather than a geological accident.