In a field of flat pasture outside Bohergar in County Limerick, a circular enclosure once occupied roughly forty metres of ground, its boundary marked by a ring of trees. By the time anyone came to record it properly, it was already gone, levelled into the surrounding farmland and invisible to inspection. The trees, the earthwork, any trace of whatever structure once defined the space: all of it absorbed by the field.

The enclosure appears on the 1923 Ordnance Survey six-inch map, which is often the last reliable record for monuments of this kind before agricultural improvement erased them in the twentieth century. Circular enclosures of this general type are a familiar feature of the Irish landscape and usually refer to a ringfort, a form of enclosed farmstead common from the early medieval period, roughly the fifth to the twelfth centuries, in which a family or small community lived within a raised bank and ditch for security and to define their territory. Whether that is what stood at Bohergar cannot be confirmed from what survives, but the size and form are consistent with that tradition. The site was compiled by Denis Power and uploaded to the record in June 2013, by which point there was nothing left to describe beyond what the map had already said.

The location itself is unremarkable to look at now, sitting in open pasture with good visibility in all directions, which is actually a quality that would have made it a sensible spot to settle in the early medieval period. If you go looking, bring the 1923 OS six-inch sheet rather than a modern map, since the enclosure will not appear on anything more recent. What you are really visiting is an absence, the negative space where something once was, legible only through the contrast between the document and the ground.