A stretch of uncoursed limestone wall, roughly twelve metres long and nearly four metres high on its outer face, now forms the northern boundary of a disused graveyard on the western bank of the River Barrow in Athy. Set into it are the splayed reveals of a blocked window, and a separate window has been lifted out entirely and built into an adjoining garden wall, where it sits somewhat incongruously among the domestic stonework. These fragments, along with scattered pieces of dressed limestone and granite in the graveyard itself, are almost certainly what remains of a medieval priory that once served the sick and the travelling poor of a busy Kildare market town.

The institution was founded by Richard de St Michael, Lord of Rheban, as the Priory of St Thomas and Hospital of St John, run by the Fratres Cruciferi, a religious order whose members, sometimes called the Crutched Friars, took their name from the cross they bore as part of their habit. The foundation date is uncertain: some sources place it in the reign of King John, between 1199 and 1216, while others point to 1253. A document from around 1270 to 1280 describes the place formally as the Priory of St Thomas the Martyr, noting that it housed brothers, sisters, and the sick. The priory sat on or just inside the line of Athy's town defences, which placed it at the edge of the medieval settlement rather than at its centre. By 1540 it had been dissolved, as happened to religious houses across Ireland and England under the Reformation, though no record survives of what the priory possessed at that point. A deed drawn up in 1603 sheds a little retrospective light: it notes that back in 1568, a man named James Foster had been granted the priory's remains, which by then comprised a church, a hall, a garden, a stable, five cottages, and a ruinous tower. The tower was already gone, in other words, within a generation of suppression. What survived after that was gradually absorbed into later buildings or broken up for building material, until the site settled into its present arrangement of a modern monastery, a private house, and the graveyard with its enigmatic wall.