What remains today are the north and east walls of a medieval tower house, rising four storeys high with their distinctive sloping batter and well-preserved corner stones. Each floor features embrasures with narrow windows cut into the thick walls, though much of the castle’s internal features, including the original entrance, stairs, fireplaces and garderobes, have been lost to time.

The history of Kilcavan stretches back to 1247 when Henry, son of Philip, held the lands as a knight’s fee from the Bigod estate. The property passed through generations of Fitzhenrys (later spelled Fitzharris), with John holding it from the Valence property in 1324 and Matthew Fitzhenry possessing it around 1420. The castle itself appears in records from 1607, when Thomas Fitzhenry died as its owner. By 1640, according to the Civil Survey, Thomas Fitzharris had become a substantial landowner with 1,160 acres spread across most of Kilcavan parish, though he would lose these lands during the Cromwellian confiscations, receiving just 300 acres in Connacht as compensation in 1656.

Archaeological evidence reveals that the tower house wasn’t a solitary structure; the flashing marks on the eastern wall show where a large single-storey building with an attic once adjoined the tower. Part of this extension’s original south wall, measuring 0.7 metres thick, has been incorporated into a small house that now stands beside the tower ruins. This later dwelling preserves an intriguing architectural detail: what appears externally as a window with a square hood moulding is actually a blocked pointed doorway from the medieval period. About 400 metres to the southeast, the ruins of Kilcavan parish church complete this cluster of medieval structures that once formed the heart of the Fitzhenry estate.