Carved stone heads look out from the north and south walls of the tower, quiet and easy to miss, while Lambay Island sits in the middle distance across the water. The tower's exterior is battered, meaning the walls angle slightly inward as they rise, a technique used to add structural weight and stability at the base, and the whole thing has a compactness about it, the interior measuring just 3.5 metres by 2.3 metres across three floors.

The church itself, dedicated to St Catherine, is a straightforward rectangular structure with an undivided nave and chancel aligned east to west, measuring roughly 15 metres in length. Entry is through a round-arched doorway set into the western end of the south wall, and the interior receives light through two narrow window openings with chamfered limestone jambs. The north side of the building has been substantially rebuilt at some point, and the chancel end is slightly inset along that wall. A wide east window survives only at sill level. The tower's west window retains Y-shaped tracery, the forked decorative stonework familiar in late medieval ecclesiastical buildings. By 1630 the church was already described as a ruin, and the Civil Survey of 1654 to 1656 records it simply as an old parish church on the farm at Portraine, suggesting it had long since fallen out of regular use by that point.

The graveyard lies just north of the road through Portraine village and is not difficult to locate, though the site is modest in scale and easy to pass without stopping. The carved heads on the tower walls reward a slow look, and the condition of the battlements, flagged in a 2011 structural survey as suffering from mortar wash-out, is a reminder of how quietly these smaller ruins deteriorate without intervention. The views toward Lambay Island are clearest in the colder months when coastal haze is less of a factor.