It measures roughly forty metres in diameter and may consist of two or even three concentric earthen banks, a form known as bivallate or trivallate, where successive rings of raised ground mark out a defined sacred or settlement space. What makes it quietly arresting is what those rings probably contain: an early cemetery, older than the graveyard beside it, pre-dating the more visible elements of the ecclesiastical complex and quietly absorbed into the landscape over centuries.

The enclosure was identified not by digging but by looking, specifically through remote sensing carried out by the Discovery Programme in 2009. Remote sensing in this context typically involves aerial photography and related techniques that reveal crop marks, soil discolouration, or subtle changes in ground level that are invisible from the surface. The analysis, cited by Shanahan in 2013, concluded that this circular feature is probably the earliest surviving element of the Baslick site. Ecclesiastical enclosures of this kind are characteristic of early medieval Irish Christianity, when monastic and church communities defined their sanctified ground with one or more encircling banks, sometimes marking the boundary between the world of the living and a space set aside for the dead and the divine. At Baslick, the graveyard in use today appears to have grown up alongside or over the later phases of such a complex, leaving this older, rounder outline just beyond its edge.