It measures 41 metres in diameter, making it a reasonably substantial example of its type, and much of it survives in good condition, which is less common than one might expect given how many similar sites across Ireland have been levelled by centuries of agricultural improvement.

A rath is an enclosed farmstead of the early medieval period, typically dating from roughly the fifth to the twelfth century, defined by a raised earthen bank and, in many cases, an outer ditch or fosse designed to keep livestock in and unwanted visitors out. At Moanbaun, that defining bank and its accompanying fosse are clearly traceable around most of the circuit, with the exception of a stretch running from the north-east to east-north-east, where no surface trace survives. Whether this gap is the result of later disturbance or simply reflects the original layout is difficult to say without further investigation. The bank was at some point planted with trees, a practice common on Irish farmland where ringforts were kept as boundary markers or simply left alone because disturbing them carried a long folkloric risk. A number of those trees have since been cut down, and only stumps now remain among the surviving growth.