In a tillage field in Conlanstown, County Kildare, something old is hiding in plain sight. The site is a bivallate enclosure, meaning it once had two concentric circular ditches, or fosses, dug around a central space. No earthworks rise above the ground today, but the buried archaeology leaves its mark on growing crops. In dry summers, the soil above the ancient ditches retains moisture differently from the surrounding earth, causing the vegetation above them to grow at a slightly different rate. From the air, or from a satellite image, the result is a faint but readable pattern of rings pressed into the landscape.

What those rings reveal is considerable in scale. The outer enclosure measures an estimated 130 metres in diameter, with an inner enclosure of roughly 60 metres sitting concentrically within it. Enclosures of this type, sometimes called ringforts or raths when they survive as earthworks, were among the most common settlement forms in early medieval Ireland, typically dating from around the sixth to the twelfth century, though some are considerably older. The double-ditched arrangement here suggests this was no ordinary farmstead. Bivallate enclosures are generally associated with higher-status occupation, the extra fosse providing additional security or perhaps marking social distinction. The cropmarks became known through aerial and satellite observation, with their presence on Apple Maps noted as recently as 2015.