No earthwork rises from the ground to catch the eye of a passing walker; instead, the enclosure reveals itself only from the air, where the buried remains of its ditches cause the crops above them to grow at slightly different rates, producing faint circular marks visible in aerial photography. This phenomenon, known as a cropmark, is one of the quieter ways that the Irish landscape keeps its past just below the surface.

What the aerial photographs show is a bivallate subcircular enclosure, meaning it was originally defined by two concentric banks and ditches rather than the single ring more commonly associated with the rath, or ringfort. Raths were the typical farmstead enclosures of early medieval Ireland, built and occupied roughly between the fifth and twelfth centuries, and they appear in their thousands across the country. This one at Coolerin sits on a gentle south-facing slope, with a small stream running northeast to southwest about a hundred metres to the southeast. Its interior measures roughly forty-five by fifty metres, with an overall external diameter of around sixty metres. A second rath survives approximately two hundred and sixty metres to the north-northeast, which suggests the area once supported more than one enclosed settlement in relatively close proximity, a pattern not unusual in the Irish countryside but easy to overlook when neither site is prominently visible at ground level.