8 metres of accumulated urban earth, there may still be a well that was once considered one of the most sacred sites in the city. Known variously as the Fountain of Dublinia and the Fountain of St. Patrick, it does not appear in any accessible form today. There are no surface remains, no commemorative plaque marking the precise spot, and the feature noted on the 1863 Ordnance Survey 25-inch map as 'St. Patrick's Well (Site of)' has long since vanished beneath successive layers of city life. The well shown inside the cathedral's south transept, sometimes offered to visitors as a substitute, was firmly dismissed by the antiquarian Drew in 1891 as nothing more than shallow drainage water collecting in a hollow, less than seven inches deep, with no claim to antiquity or sanctity.

The written record of the well stretches back at least to 1509, when a proctor named Andowe described a nearby prebendary's house as situated 'juxta fontem Sancti Patricii', beside the fountain of Saint Patrick. A manuscript by Dr. John Lyon, compiler of the Novum Registrum of Christchurch, placed it within the outer court of the Archdeacon of Glendalough's cloister. Archbishop Ussher saw it around 1590, by which point it had recently been enclosed within private houses and obstructed from view. James Malton, writing in 1790, believed it still lay under the hall of the house closest to the west end of the cathedral. Those houses were eventually cleared by the Wide Streets Commission in 1824. Drew noted that seven centuries of urban accumulation had raised the surrounding ground level by at least six feet above its medieval surface, leaving open the possibility that the well itself remained physically intact below. In 1901, excavations in the area uncovered a granite stone inscribed with an ancient Celtic cross, interpreted at the time as a marker for the original well site. The founding legend of the well, recorded by Jocelin of Furness in his medieval life of the saint, describes Patrick striking the earth with his staff in response to a woman's complaint that the nearby river ran salt with the tide, producing a fresh spring that was said to heal many infirmities.

The site today sits on the north side of St Patrick's Cathedral, along St Patrick's Street. There is nothing to see at ground level, and the well's location can only be approximated from historical maps and textual references. The 1863 Ordnance Survey depiction offers the clearest cartographic fix. Visitors curious about the area's layered past might find it useful to look at that map beforehand, if only to appreciate the strangeness of standing on a street that has grown upward by nearly two metres since the well was last reliably documented.