The impression, described as deeply marked, was left, so the story goes, when St. Columcille knelt to drink from the water during a journey across the Dublin Mountains. The well also carries a peculiar local belief, noted with dry scepticism by Handcock in 1877, that its water cannot be made to boil. Nobody, he admitted, had actually tested this.

The site is dedicated to St. Columcille, the sixth-century monk associated with Iona and Derry, and it sits within the parish of Tallaght, roughly a hundred yards from the road near the gate of Orlagh College. When Handcock visited in the 1870s, the old thorn trees around the well were hung with rags, ribbons, and garlands, the customary offerings left at holy wells across Ireland as part of devotional visits known as patterns. A granite cross standing some 60 metres to the north-east was erected around 1849, along with several others in timber and stone, in response to the cattle plague of that period. By the time Caoimhín Ó Danachair recorded the site in 1958, the spring had been enclosed in a masonry cupola and equipped with a chained metal cup; crutches left by those who believed themselves cured were noted alongside medals nailed to an overhanging tree. Folklore collected from St. Mary's School, Tallaght, recorded that during the First World War a pilgrimage was organised here specifically to seek the saint's intercession against the introduction of conscription in Ireland.

The well is located close to the entrance to Orlagh College, at the foot of the Dublin Hills. It is still actively venerated; the Sunday following the 9th of June, Columcille's feast day, draws public prayers and hymns. Visitors will find a statue of the saint, a crucifix, and the enclosed spring with its granite basin, which measures roughly 0.65 metres wide and 0.2 metres deep. The rock bearing the reputed knee-impression is at the well, and the 19th-century granite cross to the north-east is also worth locating. Small offerings, medals, and flowers are still left by those who come to drink the water or apply it to sore eyes, ears, or throat.