It is not a fragment or a slab but something closer to a pillar, roughly square in cross-section and standing about 0.9 metres tall by 0.4 metres wide, and every surface of it is covered in the kind of abstract decoration that Irish metalworkers and stone-carvers were producing somewhere around the last few centuries before the common era. The motifs are the familiar vocabulary of the Irish Iron Age: spirals, double spirals, trumpet curves, triskeles (three-armed pinwheel forms), lentoid or lens-shaped elements, and a zig-zag or step pattern, all worked into a composition that reads differently depending on which face you study.

The stone's journey to Kildare Street was long and indirect. At some point, probably well before anyone was keeping records of such things, the carved pillar was built into the fabric of the castle at Mullamast in County Kildare. Mullamast is a place with a dark history entirely separate from the stone itself, but the castle was eventually demolished in the nineteenth century, and it was during that demolition that the carved stone was recovered and recognised for what it was. The antiquary FitzGerald documented it in a paper published between 1903 and 1905, and the year that paper appeared was also the year the stone was formally transferred to the National Museum, where it has remained since.

The stone is held in the collection of the National Museum of Ireland at its Archaeology branch on Kildare Street in Dublin city centre. Admission to the museum is free. Because carved stones of this kind are not always on prominent display, it is worth checking with museum staff about the current location of the piece within the galleries, as objects can move between exhibitions or storage. The decoration is best appreciated by moving around the stone rather than viewing it from a single angle; the interplay between the trumpet curves and the spiral forms becomes clearer when you can see how the carver treated each face as a related but distinct composition.