The enclosure at Tristernagh, known on the 1837 Ordnance Survey six-inch map as Templecross Burying Ground, traces a near-perfect sub-circular outline, roughly fifty metres across in both directions. That geometry, an earth and stone bank later reinforced with a post-medieval stone wall, is the kind of boundary associated with Early Christian ecclesiastical enclosures, the roughly circular sanctified precincts that surrounded early Irish churches and their associated communities. When a graveyard retains this shape into the modern era, it often signals that the ground has been continuously respected and used since perhaps the sixth, seventh, or eighth century, the original circular form preserved simply because people kept burying their dead there.

The site sits on a low rise with open views in every direction, a placement that itself echoes early medieval practice, where elevated, visible ground was frequently chosen for sacred use. At the centre stands the ruin of a church, and in its south-western quadrant the base of a cross survives. The curving boundary of the enclosure was captured clearly in an aerial photograph taken by Cambridge University in 1969, which makes visible from above what can be harder to read at ground level. Tristernagh Abbey, a separate medieval monastic foundation, stands about 570 metres to the north-east, suggesting this part of County Westmeath accumulated religious significance over several centuries and across more than one phase of Christian settlement.