It is a circular arch, nearly two metres wide and three metres high, built from rough stone blocks set in mortar. What gives it a particular quality of quiet mystery is the keystone on its outer face, which carries the inscription "D NE 1738" alongside what appear to be initials. Someone thought it worth marking the year of construction, or perhaps the year of some significant moment in the life of whoever commissioned the work, though the precise meaning of the letters has not been firmly established.

The archway was almost certainly part of a larger enclosure, either a courtyard or an associated building connected to the nearby tower house. Tower houses, the compact fortified residences that were built across Ireland from the fourteenth century onwards, were frequently accompanied by a bawn, an enclosing wall that protected outbuildings, animals, and people in times of trouble. By 1738, however, the defensive era of the tower house had long passed, and what was being built or rebuilt here may have been more concerned with order and appearance than with security. The hanging eyes, iron fittings set into the internal face of the arch on either side, would have supported the hinges of a gate, suggesting this entrance was still functional and perhaps even formal in character.