The one at Ballybrada, in County Tipperary, does almost none of that. It exists, in any meaningful sense, only as a large oval cropmark, a shape revealed in an aerial photograph taken on 20 August 1991. From the ground, there is next to nothing to see.

Cropmarks form when buried features, walls, ditches, or banks, affect the growth of crops above them. Soil over a filled ditch retains more moisture and nutrients, causing plants to grow taller and greener; soil over a buried wall does the opposite. Viewed from the air under the right conditions, these differences in growth resolve into shapes, and shapes suggest structures. The photograph in question, reference GB91.EN.23, captured just such a moment over the low ridge at Ballybrada, where the enclosure sits on level ground amid undulating terrain that has long been worked as tillage. A slight rise in the western quadrant of the field may correspond to the edge of the monument, a faint topographic echo of whatever was once built here, but it is tentative. A small copse of trees survives in the southern quadrant, the kind of detail that sometimes marks the presence of something older beneath.

What the enclosure was, who made it, or when, the aerial image alone cannot say. It belongs to a broad category of features, circular or oval boundaries that in Ireland can date from the Bronze Age through to the early medieval period, serving purposes ranging from settlement to ritual. At Ballybrada, the ground holds its information close, and what is known comes almost entirely from one photograph taken on a particular August afternoon more than thirty years ago.