http://www.clanfagan.com/fagan-information/historical-locations
Feltrim Hill is located approximately 2 miles on the Dublin Road. There is not much left of the Hill and the well appears vanished. This was once “The Hill of the Wolves” but has been scoured by quarrying. In 1947 an Archaeological excavation was conducted resulting in over 500 artifacts including Roman coins, and a 4th-century tinned bronze mount. Here stood a 1429 “Ten Pound Castle” also called “Feltrim Castle” associated with the Fagan family. In 1574, Sir Christopher Fagan allowed Gerald – the Earl of Desmond to escape albeit a prisoner on parole. In 1690, King James stayed with Richard Fagan after fleeing from the Battle of the Boyne. Beginning in the 1700’s the Fagan family suffered an eclipse leading to the demolition of the castle by the mid-1800s. Apparently, Fagan’s well was in a good state of preservation even at that time.
Much lore surrounds the hill, ranging from apparitions of a grey ghostly horse, a big black dog with blazing eyes, and a hold hag with bundles of faggots gliding towards the Holy Well. It is said the well was originally dedicated to St. Werburgh, a Saxon princess who ruled in 689 C.E.
As far back as the 1880s, Feltrim Hill was stripped on livestock rocks for road construction. By the 1960s the stone was used for airport runways.
In the avid use of the well, especially during penal times, it was a place where Mass was held. There were noted to have been 14 beech trees on the hill leading to the well, and a mound that was likely a passage grave, all but destroyed over 60 years ago. Apparently, a limekiln still stands on the site.
Fingal Independent undated “Feltrim hill a place of peace, intrigue, and great tradition”. Website referenced 1/14/2014. http://www.independent.ie/regionals/fingalindependent/news/feltrim-hill-a-place-of-peace-intrigue-and-great-tradition-27769581.html