The Church of Ireland graveyard, designated as National Monument number 139, contains layers of history spanning centuries. A modern church now stands where an older structure once dominated the site; this earlier church, demolished in 1828, was an impressive building measuring 52 feet by 21 feet with walls three feet thick and rising between 12 and 14 feet high, complete with a vaulted, arched tower at its western end.

The real treasure of this site lies beneath the surface. Just south of the present church, visitors can access a remarkable souterrain through a modern entrance that leads down a circular shaft nearly two metres deep. This underground complex consists of three interconnected chambers with sophisticated construction techniques including corbelled walls and lintel roofing. The central chamber stretches 5.6 metres east to west and contains doorways leading to both eastern and western chambers. Particularly fascinating is a reused cross slab incorporated into the roof of the eastern chamber, bearing an incised circular design with a straight stem, though much of its detail remains obscured. The western chamber extends for 8.7 metres and shows evidence of what may have been the original entrance, with stepped roofstones suggesting an ancient access point.

Scattered throughout the graveyard are several important cross slabs that speak to the site’s long Christian heritage. These include horizontal graveslabs with Latin crosses featuring distinctive bar terminals, and more elaborate pieces like a broken cross slab standing 1.76 metres tall when complete, decorated with intricate designs including a three pointed star surrounded by L shapes, triple interlaces, and quartered circle motifs. Near the southeastern corner, another cross slab displays a Latin bar cross nested within a larger cross design, with two small incised crosses below the main arms. These monuments, combined with the site’s prominent position overlooking the valley floor and its surrounding fair pasture land, confirm Glencolumbkille’s importance as a religious centre stretching back to early Christian times.