The westernmost of all the Glendalough churches sits on a narrow shelf of land above the southern shore of the Upper Lake, hemmed in by steep cliffs and entirely cut off from the valley floor. There is no path to it. The only way to reach it is by boat.

Known as Temple na Skellig, the church is a small, single-celled rectangular structure measuring roughly 7.75 metres by 4.34 metres, partly reconstructed in the twelfth century. Its east gable holds a twin-light window, a form similar to that found at St Saviour's church in the main Glendalough complex, while the west doorway retains inclined granite jambs that once supported a flat lintel. Two fragmentary Latin crosses and several plain graveslabs survive nearby. The site is not only a church, however. To the west, excavations carried out by Henry between 1956 and 1958 uncovered a platform associated with wattle huts connected by paved paths, a kind of small residential or working settlement attached to the religious building. Those huts appear to have been destroyed by an avalanche of stone slabs, after which a wooden structure, built on a base of stones, replaced them. Finds from this later building date from the late twelfth century through to the fourteenth or fifteenth century. Excavators also recorded a charcoal layer at the site, and further charcoal-burning platforms have since been identified in the surrounding area, suggesting some form of small-scale industrial or craft activity was sustained here over a considerable period.

Because the site is reachable only by water, it retains an atmosphere of genuine remoteness that is unusual even by the standards of early Irish monasticism, which often favoured isolated or difficult terrain. Boat access to the Upper Lake is available seasonally, and the church can be seen from the water even when landing is not straightforward. The Discovery Programme has produced a 3D model of the structure, which gives a clearer sense of the building's form than photographs alone can offer.