What you are looking for is a rath, the Irish term for a roughly circular enclosure, typically dating from the early medieval period, that once served as a farmstead or defended homestead. This one at Cooltomin is barely visible in places, its bank worn down to as little as thirty centimetres on the interior side and no more than seventy centimetres on the exterior, but the outline is still there if you read the landscape carefully. Beneath it, and breaking through the surface inside the enclosure, is the raw limestone that gives this corner of Limerick its particular character.

The site sits within an area of outcropping limestone known locally as "the craggs", a landscape where the bedrock pushes up through thin soil and grazing land. The rath is roughly circular, measuring thirty-one metres north to south and just over twenty-nine metres east to west, which is a modest but not unusual size for this type of monument. The enclosing bank runs from the east-southeast to the northwest, and is best preserved along its southern and western arc. According to survey notes compiled by Denis Power, the interior surface is characterised by uneven limestone outcrops and scattered small dumps of earth and stones, the latter possibly the result of field clearance over centuries. A field boundary that once skirted the enclosure to the northwest and southeast has since been removed, and it appears that part of the enclosing element itself was lost when that boundary was taken out, which accounts for some of the erosion to the circuit.

The bank has suffered considerably from cattle grazing, as is common with raths that sit within working farmland, and this is something to bear in mind when visiting. The monument is set in pasture, so access may depend on the cooperation of the landowner. The interior is uneven underfoot, with exposed limestone making for awkward walking, and the small mounds of earth and stone scattered across it are easy to trip over if you are not paying attention. The clearest section of the surviving bank is along the south-southwest to west-northwest arc, which is where the original character of the enclosure is most legible. Early morning or late afternoon light tends to bring out the slight topographic differences in this kind of site, making the bank easier to see against the surrounding ground.