The water issues from the living rock that forms one wall of the building, crosses the chapel floor, and exits through the opposite wall before making its way down towards Lough Derravaragh below. The chapel is dedicated to a saint known as Eyen or Keyon, and the spring inside it was venerated as a holy well, a sacred water source typically associated with a patron saint and visited for healing or spiritual purposes. What makes this particular site quietly remarkable is the architecture of the thing: one entire side of the chapel is not built stone at all, but bare natural rock, making the building less a construction than an incorporation of the hillside itself.

The earliest detailed account comes from Sir Henry Piers of Tristernagh, who described both the chapel and its pilgrimage in 1682. His account, later published by Vallancey in 1786, captures the full circuit of the annual gathering. Pilgrims arrived on the first Sunday of harvest, travelling portions of the route barefoot and completing the final approach on their bare knees across stone, gravel, heath and grass. Once their devotions were done, however, the mood shifted considerably. Piers describes the congregation moving to a green area on the eastern side of the hill, where ale sellers had set up booths as at a fair and bagpipers had stationed themselves for the rest of the day's dancing and carousing. By the late nineteenth century, Reverend Cogan recorded that priests from the surrounding parishes attended to hear confessions and administer the Eucharist, suggesting the occasion had taken on a more formally ecclesiastical character by then. Locally, the well was known as Cabhra Well, and folklore collected from Carley School in Crooked Wood in the late 1930s described it as a wishing well located on the altar stone of the chapel, where visitors left pins, hairpins, garters, and copper coins. That same folklore noted that the custom of visiting on the first Sunday of August had, by that point, already ceased.