The rath at Lisnalee sits on low ground amid gently undulating grassland and bog, and its most telling feature is one that only becomes apparent when you start measuring: the northern half of the interior platform has been deliberately built up to compensate for the natural fall of the ground, so that whoever lived or worked within the enclosure had a level surface underfoot. That kind of considered earthmoving, carried out without modern machinery, speaks to a sustained investment of labour and intention.

A rath is a roughly circular enclosure defined by one or more earthen banks, typically dating from the early medieval period in Ireland, between roughly the fifth and twelfth centuries, and most likely used as a farmstead or settlement enclosure. Lisnalee appears under that name on Ordnance Survey maps from both 1838 and 1919, suggesting the local memory of the site was continuous enough to preserve its name across centuries. The enclosure measures approximately thirty metres across, enclosed by an earthen bank that varies in width from just under three metres at the south to nearly three and a half metres at the north. The external height of that bank reaches two metres on the northern side, giving the structure a more substantial presence from outside than from within. On the eastern and south-eastern arc, the bank has been worn down to little more than a scarp. A two-metre gap at the south-west, at the lowest point of the bank, may mark the original entrance. The bank's near-vertical outer face suggests it was reworked at some point in the relatively recent past, though what prompted that modification is not recorded. A second rath sits on higher ground roughly 225 metres to the north-north-east, hinting that this stretch of Mayo was once more densely settled than its present quietness would suggest.