A clochan, as these corbelled stone structures are known, is constructed by laying courses of flat stones so that each ring slightly overhangs the one below, until the walls curve inward and close at the top. This one, on High Island, is unusually well preserved, and the excavations that revealed it in full have made it one of the more closely studied examples of its type in the west of Ireland.

Before excavations beginning in the mid-1990s, the lower exterior was buried under grass-covered rubble, concealing much of what turned out to be a sophisticated piece of early medieval engineering. Work led by Scally established that the building is almost square internally, measuring roughly 2.8 metres east to west and 2.7 to 2.8 metres north to south, with walls between 1.5 and 1.7 metres thick on most sides. The corbelling begins at about 0.8 metres above the floor, where the large rectangular boulders of the lower courses give way to smaller stones that step inward to create the characteristic domed interior, rising to a maximum height of 2.8 metres. The low, splayed doorway in the east wall is framed by three lintels, the innermost of which is a reused cross-slab; the north jamb stone is possibly another, and a third broken cross-slab was laid into the paved floor. These fragments, repurposed as building material, suggest the community was drawing on an older layer of carved stonework already present on the island. Possible wall cupboards survive in the north and west walls. Beneath the floor, excavators found evidence of a smithing hearth, and radiocarbon dating placed the metalworking activity somewhere between the late ninth and early eleventh century, meaning the forge pre-dates the clochan itself. Scally dates the building of the clochan to the mid to late eleventh century and suggests it may have functioned as a communal space for the preparation and sharing of food.