The site at Ballinlass in County Galway goes by the name 'Lisduff' among people in the area, a name that translates roughly from the Irish as 'black fort' or 'dark enclosure', and which quietly insists on a significance the ground itself no longer makes obvious. What survives above the soil is modest: a subcircular earthwork roughly 33 metres across on its north-to-south axis, sitting on an east-facing slope in gently undulating grassland. The defining features, a scarp, an intervening fosse, and an outer bank, are clearest from the northern arc around through the east to the south-east. Elsewhere, only a slight rise in the ground marks where the monument ends.

This is a rath, the most common type of early medieval enclosure in Ireland, typically built between around 500 and 1000 AD as a farmstead for a single family or small community. A fosse is simply a ditch, usually dug to reinforce the bank thrown up beside it. At Lisduff, the earthworks have suffered over time. A field wall, constructed at some point after the rath fell out of use, cuts directly across the fosse and outer bank on the southern side, which accounts for some of the deterioration. The overall shape is still legible, but only just, and the northern and eastern portions offer the clearest sense of what the original enclosure once looked like in plan.