It is a fully formed semi-circular arch, over three metres tall and nearly as wide, with carefully cut jambs and voussoirs, the wedge-shaped stones that lock an arch into place. Punch dressing covers every visible surface, a technique that leaves a stippled, worked texture on the stone face, and the long jamb on the western side retains a neat plain margin with two rows of tooling. Curvilinear hanging eyes and squared spud stones, the fittings that once held a gate on its hinges, are still present on both sides, and a pair of double-leaf wrought iron gates currently hang from them, giving the impression of something purposeful and in use. The threshold stone, however, tells a different story: it sits level with the ground on one side and raised above it on the other, resting on courses of walling, suggesting the whole structure was set down here rather than grown from this spot.

The gateway is thought to date from the sixteenth or early seventeenth century, and its original home was almost certainly a bawn, the fortified stone enclosure that typically surrounded an Irish tower house of that period, protecting the household, livestock, and stores within a walled yard. At some point it was dismantled and re-erected roughly three hundred metres north of Peppardstown House, apparently as a decorative entrance feature. Peppardstown House itself is a multi-period building; its oldest section, to the rear, appears to date from the eighteenth century, with a later nineteenth-century front. The gateway, then, is considerably older than either phase of the house it was brought to ornament, and the wall into which it now sits, a stretch of roughly coursed limestone rubble running over eight metres with well-dressed quoins at each end, was likely built around it to give the arch its proper context. Whether there was ever a plan to make practical use of the gateway is unclear; local tradition holds that there was not.