The well, known locally as Tobernea, pronounced "Tober-Nay", consists of a brick-built vault over a chamber that leads into a lintelled recess, a horizontal stone-capped opening set into the rock face. Beyond that recess there was once a further inner passage, though that opening is now blocked. The water feeding it comes from a subterranean rivulet that trickles through a cleft in the granite hillside above, emerging in a space so narrow that a photographer writing in 1901 noted he could not position his camera more than two feet from the aperture.

The name Tobernea points to a dedication to a specific early Christian figure. The local pronunciation suggested to researchers that the well was associated with someone named Noe or Nathí, and it is possibly connected to St. Nathí of Taney, a church site whose Irish name, Teach Nathí, survives in the modern placename Dundrum. Holy wells in Ireland were typically associated with a patron saint and visited on that saint's feast day, with prayers and rituals performed in a set circuit. The healing tradition at Tobernea was focused on the eyes: a Mr. Gaffney of Chapel Lane, recorded in 1901 as having lived in Blackrock for over sixty years, recalled neighbours bringing vessels to carry the water home and wash their eyes with it when suffering from complaints of the sight. By the time O'Reilly wrote about the site in 1902, the practice was already fading, and the site is no longer venerated.

The well sits on the cliff edge overlooking a grassy field adjacent to the coastline, in the parish of Monkstown, south County Dublin. The landscape around it has been shaped by land reclamation, what the 1901 account describes as "reclaimed slob-land", low-lying ground recovered from tidal mudflats. The railway line running close by is a useful orientation point for anyone trying to locate it. The structure itself is modest and easily overlooked; the brick vault is partially covering rather than fully enclosing the chamber, and the inner passage that once extended further into the rock now ends abruptly. What remains is a quiet, compressed piece of early devotional geography, set into a granite hillside with the sea close enough to hear.