A preceptory was a local administrative house of the Knights Hospitaller, the medieval military-religious order that combined the care of pilgrims with armed force, and this one is unusual in that its enclosing walls, towers, church, and the ghost of a second internal building all survive in some legible form, if only barely. The whole enclosure is roughly wedge-shaped in plan, about 90 metres along its main axis, with the church and its still-active graveyard occupying the northeastern portion.

The house was founded around 1200, and the church that stands at its centre is a substantial structure: a nave roughly 30 metres long with a chancel added to the east end, connected by an arch of which only the springings now remain. The nave walls contain a curious row of small square holes running at about chest height; they are most likely putlog holes, the sockets used to anchor scaffolding during construction, though an early twentieth-century commentator named O'Regan proposed in 1901 that they once held sliding panels to ventilate the interior. By 1335 the Hospitallers were sufficiently concerned about security that a Brother John FitzRichard, on his appointment to Mourne, was formally required to build a fortified tower there. That tower still stands at the southwestern corner of the enclosure, its vaulted ground floor partly intact and a fragment of fireplace surviving at first-floor level, though its entire western side has fallen away. A second, D-shaped tower at the northwestern corner survives only as low stumps. Writing in 1750, the historian Charles Smith described the southern side as having been defended by a strong castle that was then still largely standing, and noted that much of the enclosing wall had recently been demolished, the stones carted off to repair the local turnpike road. No trace of that southern castle remains. By the sixteenth century the preceptory had passed out of Hospitaller hands entirely and into those of the Mac Carthy family. There are also references in various sources to a medieval settlement called Mourne, Mora, or Ballymona somewhere in the vicinity, and a murage grant, which was a royal licence to collect tolls for the building or upkeep of town walls, was issued in 1317, but where exactly this settlement stood remains uncertain.

The site sits just off the roadside, and the graveyard portion is still in use, which means access to at least part of the enclosure is relatively straightforward. The church walls stand close to full height in places, and the southwestern tower is worth examining closely for its vaulting and the remnant of the mural chamber tucked within the vault's haunches. The rest of the enclosing wall, where it survives, runs along the east bank of the stream and gives a reasonable sense of the original scale of the complex, even where ivy and vegetation have done their best to reclaim it.