The burial ground at Aghaviller sits on a gentle rise with the land falling away to the north, and when the first Ordnance Survey six-inch map was drawn up in 1839, it recorded something that has since quietly disappeared: a dashed line extending the graveyard northward by around 32 metres beyond its enclosed boundary, marking an area that was unenclosed but apparently still considered part of the burial ground. That northern extension now lies within the garden of the house immediately to the north, with no visible signs of burials at ground level. Whether the land was ever used for interment, or simply anticipated for it, the cartographers noted it as something distinct from ordinary ground.

The graveyard is roughly rectangular, running about 55 metres northeast to southwest and 33 metres across, with the public road forming its eastern edge. It is not the dimensions that make Aghaviller worth attention, however, but its immediate company. A round tower, one of those tall, tapering stone structures built from around the 9th century onwards and associated with early monastic sites, stands close to the western boundary wall. The northern boundary of the graveyard is formed by the surviving north wall of a church that dates, in its origins at least, to the 12th or 13th century, though it has been heavily modified since. According to the historian William Carrigan, writing in 1905, the church was dedicated to St Brendan of Birr, a 6th-century Irish monastic founder distinct from the more widely known Brendan the Navigator. A holy well dedicated to the same saint lies roughly 220 metres to the northwest of the church. Headstones in the graveyard run from the 18th century up to the present, giving the site a continuity of use that stretches across several centuries of the same landscape.