In a field at Ballyfair in County Kildare, something circular lies buried beneath the soil, invisible from the ground but legible from the air. It shows up as a cropmark, a faint but telling difference in the colour and growth of crops above it, caused by buried features such as ditches or banks that alter how moisture and nutrients move through the earth. In this case, the mark traces a roughly circular enclosure around thirty metres in diameter, the kind of shape associated in Ireland with ringforts, burial monuments, or other enclosed settlements dating anywhere from the Bronze Age through to the early medieval period.

The enclosure was first recorded on an aerial photograph taken in 1969, when tillage farming had left the ground in the kind of condition that makes cropmarks most legible. Decades later, a 2010 orthophoto, a geometrically corrected aerial image used in mapping, caught a faint echo of the same outline, suggesting the buried remains are still largely intact beneath the ploughsoil. That the feature appeared at all in the later image is itself notable; cropmarks are notoriously inconsistent, dependent on the right combination of crop type, soil moisture, and season to reveal themselves.