Known locally as Teampall Chiaráin, it sits on a terrace above Port na Mainistreach on the island's northern shore, and its walls carry the marks of at least three distinct building phases layered onto one another without apology. The west gable has a trabeate doorway, meaning the opening is spanned by a flat horizontal lintel rather than an arch, a technique associated with early Irish church building. The east window, by contrast, is transitional in style, reflecting the shift from Romanesque to Gothic that took place around the twelfth century, while a pointed-arch doorway cut through the north wall belongs to a later medieval phase entirely. Few sites in the west of Ireland make the long stretch of Irish ecclesiastical building so legible in so compact a space.

The monastery here was founded in the sixth century and is attributed to St Ciarán, one of the Twelve Apostles of Ireland, a grouping of early monastic figures said to have studied under Finnian of Clonard before dispersing to found their own communities. The site preserves considerably more than the church alone. Three further ruined buildings stand in close association with Teampall Chiaráin, and to the west-northwest lies a holy well, a type of site that in Ireland typically marks a place of pre-Christian or early Christian veneration that continued in use across many centuries. Also present are a sundial, a cross-inscribed pillar, and two further standing pillars that may have functioned as termon markers, stones that in early Irish ecclesiastical law defined the boundary of sanctuary land belonging to a monastery, within which certain legal protections applied. A cillín, a small burial ground often used for unbaptised children or others excluded from consecrated burial, lies in the fields to the north-east and east-north-east, a quiet reminder of the long social life of these ecclesiastical enclosures well beyond the medieval period.