At Pollaweela in County Mayo, a circular embanked enclosure, somewhere between 25 and 30 metres in diameter, was recorded on the Ordnance Survey's six-inch map of 1838 and then effectively ceased to exist. Not through any dramatic event, but through the quiet accumulation of time and change. Later map editions omit it entirely, and at ground level there is nothing to see. A house now partly covers the spot.

The 1838 OS six-inch series was a remarkable undertaking, one of the most detailed cartographic surveys of any country at that period, and it captured features that subsequent generations would alter or lose. The enclosure it recorded at Pollaweela was a circular embanked type, a form common across Ireland and typically associated with early medieval settlement, though such enclosures can span a wide range of periods and functions. They consist of a raised bank of earth defining a roughly circular area, often the remains of a farmstead or small defended homestead. Whatever this particular example once enclosed, it sat on a level area of pasture with a break of slope to the west and north-west, a position that would have offered some natural advantage in drainage and outlook. By the time later surveyors returned, it had gone from the landscape record, absorbed into the working land around it.