Most raths, the circular earthen enclosures built across Ireland during the early medieval period roughly between the fifth and twelfth centuries and used primarily as farmsteads by farming families of some local standing, are single unified spaces. This one, sitting in level pasture at Frenchbrook in County Mayo, contains a second, lower bank running northeast to south through its interior, dividing the enclosed ground into two unequal portions. That subdivision is unusual enough to give even a casual observer pause.

The enclosure itself is a raised, roughly circular platform measuring around fifty metres north to south and fifty-six metres east to west, with the central raised area standing about one and a half metres above the surrounding ground. An earthen bank roughly a metre high encloses it, though this has been levelled along the southern to northeastern stretch. The internal bank is lower, at around seventy centimetres, and its purpose is not certain. It may reflect a later modification to the original layout, a practical division of space for livestock or storage, or it may preserve evidence of phased construction. A survey of Ballinrobe and its district, compiled by D. Lavelle and published in 1994, recorded the site as part of a broader look at the archaeology of the area around Lough Mask and Lough Carra, and it is from that record that these details survive.