At Ballindrehid in County Mayo, a roughly circular earthwork sits in low-lying, somewhat neglected pasture, its outline so eroded that it never made it onto any edition of the Ordnance Survey six-inch maps. It only entered the formal record at all because an aerial photograph caught what the ground obscures: a circular form, around sixteen metres across, that looks like something deliberate once stood here.

The feature is classified as a possible enclosure, a broad term in Irish archaeology that covers everything from ringforts, which were enclosed farmsteads typically dating from the early medieval period, to much earlier prehistoric settlements. What survives at Ballindrehid is a fosse, a defensive or boundary ditch, visible now as a shallow depression widening slightly from north to south, most legible along its south-western arc. On the inner edge of the fosse at the south-west, there is a short length of stony bank, two metres long and rising to about a metre in height, which may be the last remnant of an enclosing wall or rampart, though the ground gives no certainty. Outside the fosse to the north-west, a slight rise and a patch of rougher vegetation suggest a possible outer bank, though it disappears before it can be confirmed. Inside the enclosure, two roughly circular depressions have been dug into the northern sector, the larger about four metres across, the other slightly smaller and shallower just to the south. Their purpose is unknown. A derelict farmstead lies a short distance to the south-west, and a ridge visible to the north-east gives the site a quiet sense of orientation, even if the earthwork itself seems to be gradually returning to the field around it.