The approach itself is lintelled, meaning flat stone slabs are laid horizontally across upright supports to form a kind of roofed corridor, a construction method more commonly associated with prehistoric tombs and early medieval souterrains than with a simple water source. That a well should be reached this way, through a deliberate architectural threshold in the middle of an ordinary field, gives the site an atmosphere quite out of proportion to its modest scale.

The well is recorded in the National Monuments Inventory as O'Grady's Well, a name that suggests a long association with a particular family or local figure, though the structure itself is thought to be medieval in date. Holy wells and covered water sources of this kind were often focal points for religious observance, patterns, and local tradition throughout medieval and early modern Ireland, and many retained their importance in local memory long after the formal ecclesiastical structures around them had disappeared. The site at Barnacullia was compiled and documented by Geraldine Stout and Padraig Clancy, with a revised record uploaded in July 2018, suggesting it has attracted at least some scholarly attention in recent years.

Barnacullia sits on the lower slopes of the Dublin Mountains near Sandyford, and the surrounding area is a mix of residential edges and open hillside. The well lies in a field rather than in any managed heritage site, so access requires a degree of local knowledge and consideration for the landowner. There are no facilities or signage to speak of. The stone covering and lintelled passage are the things to look for; the passage in particular is easy to overlook at ground level, especially in summer when vegetation thickens around field boundaries. Going in drier months, when the ground is firmer and the stonework more exposed, makes the approach easier and the structure itself more legible.