A ring barrow is a prehistoric burial monument, typically of Bronze Age date, consisting of a low mound surrounded by a shallow ditch, or fosse, and an outer bank of upcast earth. At Coolagh, that circuit survives: the fosse runs to around 0.45 metres deep, the bank to roughly 0.47 metres high, and the whole enclosed area measures just over five metres across. A causewayed entrance, a deliberate gap left in the ditch and bank rather than a later intrusion, opens to the east at a width of 1.4 metres, suggesting an intentional orientation that was meaningful to whoever constructed it.

The monument's current appearance owes something to a long history of agricultural pressure. When Bowman recorded it in 1934, the central mound had already been levelled, though the surrounding earthen ring remained visible. His measurements, given in imperial units as was standard at the time, describe a fence or bank some 27 feet in diameter encircling what had been a mound 16 feet across at its base. The fact that the enclosing element outlasted the mound itself is not unusual; the outer bank of a ring barrow tends to be lower and broader, making it harder to plough away entirely, while the central mound, the most conspicuous part, is often the first to be reduced by generations of tillage or earthmoving. What remains at Coolagh is therefore a partial record, the frame surviving where the centrepiece has gone.