It is identified in the archaeological record as Building C, a designation that does little to suggest how much architectural detail survives in a structure of such modest dimensions, roughly 7.5 metres along its longer axis and just over 5 metres across.

The building forms part of na Seacht Teampaill, the Seven Churches, a monastic complex whose name refers to a collection of ecclesiastical remains rather than seven intact roofed structures. Built of roughly coursed mortared masonry, its walls reach a thickness of around 0.8 metres. What distinguishes it from the surrounding ruins is the quality of the surviving openings. At the northern end of the south-west wall, a pointed arch doorway remains visible, flanked on either side by a single-light ogee-headed window. An ogee arch is a curved form that combines a concave and a convex section into a gentle S-shape, a detail associated with late medieval Gothic craftsmanship and not something one expects to find so well preserved in a small ancillary building on a windswept island. The opposing north-east wall retains the remains of a second doorway, suggesting the structure was designed to allow passage through it, perhaps connecting different parts of the monastic enclosure. The building is located approximately five metres to the north-east of Temple Brecan itself, a church closely associated with St Brecan, an early Irish monastic figure connected with Inis Mór. John Waddell documented the structure in 1973, and Paul Gosling's later survey also recorded it.

The Seven Churches complex is accessible on foot from the village of Eoghanacht in the western part of Inis Mór. The ogee windows on Building C are worth examining closely once you locate the structure, as they tend to read as undifferentiated stonework from a distance.