It is barely larger than a shoebox in two of its dimensions, a rectangular stone-lined depression measuring roughly 85 centimetres east to west and only 20 centimetres north to south, with a depth of about 30 centimetres. It holds no water now, but in the nineteenth century, parents brought ailing children here and laid them within it, a practice recorded by O'Flanagan in 1930. The well is, in other words, less a well in the conventional sense and more a carefully constructed ritual space, shaped to receive a small body.

What makes Tobernatasha still stranger is one of the stones forming its edge. Set into the western side is a fragment of a cross-slab, a carved stone panel roughly 48 by 46 centimetres and 13 centimetres thick. Incised into its face is a ringed cross, the familiar form in which a circle connects the arms, here drawn in double lines. Cross-slabs of this type are associated with early medieval Irish Christianity, and the fact that this one has been incorporated into the fabric of a holy well suggests a long and layered history of sacred use at the site. Whether the slab was placed there deliberately or simply repurposed from a nearby source is not recorded, but its presence gives the well an ambiguity that feels characteristic of such places, where the boundaries between early Christian devotion and older curative traditions were never very firmly drawn.

The well sits on the floor of an east-west valley, roughly 150 metres south of Kilnamona church, and the ground around it is unremarkable enough that a visitor without some prior knowledge of its location could easily pass it by. The depression is shallow and dry, and the carved fragment at its western edge is the clearest thing to look for once you are close.