This is Trinity church, also known as the church at Brockagh, and it rewards closer attention: a nave-and-chancel building in granite, with a fine chancel arch separating the two spaces, six corbels still projecting from the exterior walls at the positions where they once carried a timber roof, and a trapezoidal cross-slab outside the south door inscribed with a small single-line Greek cross.

The fabric of the building records several phases of construction and alteration. The nave measures roughly nine metres east to west and 5.4 metres north to south, with the chancel a good deal smaller at 4.1 by 2.8 metres. A doorway in the west wall, built with the characteristic inclined jambs and flat lintel of early Irish ecclesiastical architecture, leads into a later annexe that may have served as a sacristy. This annexe had a corbelled roof, a construction technique in which stones are laid in overlapping courses to form a vault without the need for centring or mortar, and it was once topped by a small round tower or belfry. That tower was destroyed in a storm in 1818, which gives an unusually precise date to at least one moment of loss in the building's history. When the annexe was added, a round-headed door was also inserted towards the western end of the south wall, a secondary opening that slightly disrupts the original scheme. The chancel receives light from a round-headed window in the east wall and a pointed window in the south, while the nave has a single round-headed window in its south wall. Alongside the church itself, two millstone rough-outs were recorded at the site, unfinished quernstones that suggest some degree of craft activity in the vicinity of the monastery.

The site is a National Monument in state ownership and forms part of the wider Glendalough complex, though it sits apart from the main enclosure. Its position on the slope above the Glendasan river means the approach involves some uneven ground, and the church is not always as prominently signposted as the central monuments. The cross-slab outside the south door is easy to overlook, half-embedded and worn, but the incised cross cut into its surface is still legible on a clear day.