Inishtooskert lies four miles off the western tip of the Dingle Peninsula and two and a half miles north of the Great Blasket, its 241 acres rising steeply to a maximum of 573 feet above sea level. The northern half of the island shows no trace of settlement whatsoever, which makes the concentration of Early Christian remains in the southern half feel all the more deliberate, as though whoever chose this place understood exactly how remote they were making their life.

The oratory known as Teampall Bréanainn, dedicated to St. Brendan, is modest even by the austere standards of early Irish ecclesiastical architecture. An oratory, in this context, is a small stone chapel intended primarily for private prayer rather than communal worship, and this one measures just under three metres north to south and three and a half metres east to west on the inside, with walls between one and just over a metre thick. It was built without mortar, a technique known as dry-stone construction, and its walls survive to a maximum height of one metre. The western doorway is flanked by two upright stones set against the inner face of the wall, and the passage is extended on its southern side by a single standing stone, or orthostat, on the exterior. Inside, a small drystone altar is butted against the eastern wall, though this may be a later addition rather than an original feature. Immediately outside the southern wall lies a substantial mound of stone, notable for its high proportion of white quartz, measuring roughly four and a half metres by two and a half metres; a stone cross stands at its south-western corner. Quartz appears frequently in Irish prehistoric and early medieval sacred contexts, its use apparently tied to beliefs about light, purity, or ritual significance that are not fully understood.