Despite the name, only two actual churches survive within it, a discrepancy that has puzzled visitors for generations. The more substantial of the two is Teampall Bhreacáin, St Brecan's Church, and what makes it genuinely unusual is that its standing walls contain, layered within them, five distinct phases of construction spanning roughly five centuries. The building is not so much a single church as a slow accumulation of decisions, each generation of builders partly demolishing, partly reusing, and partly extending what came before.

The earliest structure, which scholars date to around 1000 AD, was a tiny single-cell building of cyclopean masonry, a technique using very large, minimally dressed stones. It had a trabeate west doorway, meaning a flat-lintelled opening rather than an arch, and this was eventually blocked up so carefully, with replacement stones matched so closely to the surrounding fabric, that it became nearly invisible. The lintel survives, set asymmetrically above where the door once was, and a carved inscription on the interior face of the same gable reads OR AR II CANOIN, a prayer for two canons. By the mid-to-late eleventh century the nave had been extended eastward, and by no earlier than the twelfth century it had been widened to the south. Then, in a fourth phase associated with a style known as the School of the West and dating from the late twelfth to the early thirteenth century, a chancel was added. Its arch is of diagonally dressed and chamfered limestone ashlar, decorated with traces of foliate ornament and a roll moulding. The ghost outlines of the two earlier east gables are still visible in the masonry above the arch. A fifth phase, in the late fifteenth or early sixteenth century, added further windows, a new south doorway, and an altar.

The church sits at the centre of a wider landscape of early Christian monuments, including high crosses, cross-slabs, cross-inscribed pillars, holy wells, and leachtaí, which are low cairn-like structures associated with prayer stations and penitential practice. Surrounding buildings are thought to have housed the religious community itself and, separately, pilgrims who came to move through this entire devotional circuit. St Brecan himself is poorly documented; he may have been a contemporary of the sixth-century St Enda, the figure most associated with Inis Mór, but whether he founded the site or simply gave his name to a later dedication remains unclear.