The valley of Fohernamanagh, or Fothair na Manach, meaning roughly 'the monastery of the monks', sits about midway between Brandon Creek and Sauce Creek at the northern end of the Brandon mountain range on the Dingle Peninsula, enclosed on every side by cliffs and mountain slopes averaging around 1,500 feet. Its ecclesiastical character is suggested less by any surviving structure than by its name and by a persistent tradition linking it to St. Brendan, the sixth-century monk celebrated for a legendary sea voyage across the Atlantic. He is said to have founded a monastery here, and also to have rested at this spot before setting out on that voyage. Whether those two traditions are versions of the same story, or distinct recollections of actual association, is impossible now to say. What is clear is that the valley's extreme inaccessibility fits a pattern well known from early Irish monasticism, in which communities deliberately sought out remote, difficult terrain as a form of physical withdrawal from the world.

The archaeology of the site is dense and not easily read. At the centre of the valley, on the only level ground, a D-shaped enclosure with drystone walls shows at least two phases of construction; in places the southern wall still stands to 2.4 metres. Inside and immediately around the enclosure are the remains of several clocháns, the small corbelled stone huts, built without mortar, that are characteristic of early Irish monastic sites, three of which appear to have been joined together. One retains three internal wall-cupboards; another, probably circular originally, was later modified into a sheep-shelter by the insertion of a straight wall across one side. On the scree-covered slopes to the south-east of the enclosure stands a more puzzling group: an oblong building, its walls still up to two metres high, connected to a partially subterranean stone-lined passage running northward. The passage, about half a metre high and just over a metre wide, no longer has its roof intact, though one large capstone has simply dropped in place. A possible second underground passage lies about 2.25 metres to the south-west. The function of both is uncertain. Despite all this, the valley is known to have been occupied by three or four families at the start of the nineteenth century, and some of what survives may reflect that later habitation rather than anything earlier.

Reaching Fohernamanagh is genuinely demanding. The approach begins with an ascent from the village of Tiduff to roughly 1,500 feet, along an old track that passes the Arraglen ogham stone, an inscribed standing stone from the early medieval period. From that height the descent into the valley follows the course of the southern gully or, alternatively, scree-strewn slopes on the north-eastern side. An early visitor, Power, arrived by sea in 1923, though by his own account that route offers little to recommend it.