What makes this particular monument quietly interesting is not just its age but the fact that it is still, in a meaningful sense, being discovered. Two orthostats forming part of a second chamber only became visible in recent years, meaning the site as it exists on the ground no longer matches the plan published in the authoritative survey of the early 1970s. The monument is, structurally speaking, a work in progress.

Court tombs are among the oldest megalithic monuments in Ireland, built by farming communities during the Neolithic period, roughly between 4000 and 2500 BC. They typically consist of a roofed gallery divided into burial chambers, fronted by an unroofed semicircular forecourt where rituals are thought to have taken place. At Garvagh, a polygonal chamber at the western end of the cairn measures 3.4 metres long by 2.5 metres at its widest point. The open northeastern end of this chamber features what are described as imbricated segmenting jambs, that is, opposing upright stones set slightly overlapping like roof tiles, used to divide or partially screen one section of the gallery from another. In front of this chamber, two orthostats, the large upright standing stones that form the skeleton of megalithic construction, mark the northwestern side of a second chamber approximately 3 metres long. Towards the northeast, further large slabs protrude from the cairn surface, though their precise relationship to the rest of the gallery remains unclear. The site was catalogued by Ruaidhrí de Valera and Seán Ó Nualláin in their 1972 survey of megalithic tombs, but the recently emerged orthostats represent a genuine revision to that record, a reminder that these monuments continue to yield information long after they are first documented.