Look more carefully, and the curve is too deliberate, the enclosure too symmetrical: a sub-oval roughly 79 metres from north to south and 49 metres from east to west, its bank rising to about one and a half metres. Along the south-western to north-western arc, the bank has been levelled almost flat, but the ground still betrays a slight undulation, the landscape's way of preserving what agriculture has tried to erase. The only feature inside is a graveyard tucked into the south-western quadrant, quiet confirmation that this was once ground set apart for purposes beyond farming.

Ecclesiastical enclosures of this kind are the footprint of early Irish Christianity. Before stone churches became common, religious communities marked out their sacred territory with a roughly circular or oval earthen boundary, a technique with roots older than Christianity itself. The enclosure at Killasseragh is believed to be the site of St. Lasser's Church, a dedication that appears on the six-inch Ordnance Survey map of 1936, by which point the building itself had long since vanished. St. Lasser, also known as Lasair, was a female saint associated with several sites in Ireland, and a dedication in her name hints at the kind of local cult that once gave these small enclosures their meaning and their community. About 300 metres to the south-south-west, a megalithic structure survives, a reminder that the area carried significance across more than one era, and that early Christian sites were often drawn, deliberately or otherwise, to landscapes already freighted with older presence.