Yet the small D-shaped graveyard on the north-east-facing slope of what is now called Great Island, beside the silted-over channel of the Barrow and Nore, contains a remarkable concentration of early medieval stonework. Among the pieces is what may be the smallest high cross in Ireland, a sandstone carving just fifty-five centimetres tall, its solid head decorated with rope-moulding along the edges and panels of knot interlace on each face. A partial inscription, possibly reading NDMNA, runs along the top of one side. Beside it sit a circular baptismal font of conglomerate and a crude granite cross-base, its rectangular socket now empty. A sheela-na-gig, a carved figure of a type found on Irish Romanesque churches and associated buildings, was recovered from the garden of Kilmokea House nearby and is presumed to have originated in the graveyard itself.

The site has been identified as Inis Teimle, an island territory described in early sources as lying between the kingdoms of Uí Chennselaig and the Déisse, straddling what are now counties Wexford and Waterford. The church was founded in the early eighth century by a figure named Suadbar, and two saints, Findbarr and Barrfhinn, both sons of Aed with Déisse ancestry, became associated with it. The place name Kilmokea derives from the Irish Cill mac (n)Aeda, meaning the church of the sons of Aed. The site was raided by the Vikings in 822, 825, and again in 951, and it may have already been abandoned before the Anglo-Norman occupation took hold in the 1170s, though it subsequently became the centre of the medieval parish. By 1615, when Thomas Ram, the Protestant bishop of Ferns, carried out a visitation, the church and chancel recorded as Insula Harvei were still noted as being in repair.

The graveyard sits within a large ecclesiastical enclosure, roughly 330 metres north to south and 260 metres east to west, defined by an earthen bank and outer fosse that survive best on the south-west and west sides. A bullaun stone, a granite boulder with a deliberately hollowed basin used in early monastic contexts, lies in the base of the fosse at this section. A horizontal mill, its wooden flume and millstone found beside a small stream running through the enclosure around 1970, points to the practical workings of the community that once lived here. A resistivity survey in 2014 revealed hints of a further D-shaped enclosure about one hundred metres west of the graveyard, with possible traces of a large stone building inside it, though the ground there has yet to yield anything definitive.