The structure is a wedge tomb, the most common megalithic tomb type in Ireland, so called because the internal gallery is typically wider and higher at the western entrance and tapers toward the east. This one follows that pattern closely, its gallery narrowing from just over a metre wide at the west to slightly less at the eastern end, a deliberate architectural choice whose exact ritual significance is still debated but which may relate to solar orientation or the symbolic threshold between the living world and the dead.

What survives at Gortnacarriga is a gallery roughly 2.73 metres long, defined by two sidestones along the north face and three along the south, with a single backstone closing the eastern end. Inside the western entrance, two jambstones are set lengthwise, likely forming a kind of internal division or portal. Around the gallery itself runs an outer-walling, a low enclosing kerb of additional stones that is characteristic of wedge tombs and would originally have helped retain a covering cairn of smaller stones or earth. One large flat slab lying prostrate just outside the southern outer-walling, measuring around 1.35 metres by 0.8 metres, may be a roofstone that has slipped from its original position over the centuries. A second smaller slab rests within the gallery area. The tomb sits about twenty metres north of a broad natural rock outcrop, a relationship that may be incidental or may reflect a deliberate choice by the people who built it, for whom prominent geological features often carried meaning.

The surrounding landscape of undulating hills and cleared forestry gives the site an open, exposed quality that is somewhat at odds with the dense planting that covered it for much of the twentieth century. The clearance of the conifers has, in one sense, returned something like the open upland setting that would have surrounded the tomb when it was built, probably during the late Neolithic or Early Bronze Age, somewhere between four and five thousand years ago.