Dry at the time it was recorded, and modest in its dimensions, one metre wide and only thirty centimetres long, it is easy to overlook. Yet the care taken in its construction is still legible: a massive granite boulder forms the back wall, with smaller boulders arranged on either side to complete the enclosure. Whether it ever served a ritual purpose or simply supplied water to whoever lived in that now-collapsed house is an open question, but the balance of probability leans toward the domestic.

St Macdara's Island, known in Irish as Cruach na Cara, takes its name from a sixth-century saint who is said to have lived here, and the island retains an early oratory dedicated to him, one of the more complete examples of early Irish stone church architecture surviving in the west. The well sits at the south-eastern end of the island, in proximity to a ruined house that suggests a more recent, though still historical, period of habitation. Granite is the dominant building material in this part of Connemara, and the well's construction follows the same logic as countless other field enclosures and field walls in the region: use what the landscape offers, and use the largest available stone where strength and permanence matter most.