On its summit sits a rectangular structure that nobody has been able to examine closely, on account of the difficulty and danger of the approach. Local memory holds that steps once led up to it, which implies regular use at some point, though by whom and for what purpose remains unresolved. An old bohareen, a narrow country lane, leads down toward the island and toward what may have been lead mines in the vicinity.

The Pierces who gave this place its name were descendants of Piers, younger son of Thomas, the first Lord of Kerry, whose line dates to 1280. To the east of the island, an enclosure of earthen banks and a fosse, a shallow external ditch roughly six metres wide and half a metre deep, encloses a rough area of mounds, depressions, and what may be the remains of sub-rectangular structures. A fieldbank running northeast to southwest divides the enclosure unevenly, with waterlogged depressions to the west and possible building outlines to the east. The natural cliff edge to the seaward side does part of the enclosing work that the earthen bank does elsewhere. Writing in 1687, Sir Richard Cox described this stretch of the Kerry coastline near Kerry Head and the mouth of the Shannon as home to the best lead mine in Ireland, though one that was "hard to Worke because it runs into the ocean." His account mentions amethysts and emeralds nearby, a cave called Powlaglugger whose storm-noise could allegedly be heard sixty miles distant, and the lead workings that may correspond to activity around this site. A separate local tradition, recorded by a Mr John Pierse, concerns the collection of salt in the same area, adding another layer of possible economic use to a place that seems to have been productive in several ways at once, even if the specifics have blurred over the centuries.