This is the visible skeleton of a portal tomb, a type of Neolithic monument in which two tall entrance stones once framed a burial chamber capped by a massive roofstone. Many of these structures have lost their covering earthen mound over millennia, leaving only the bare stonework, which can give the impression of something impossibly poised. At Ervey, the roofstone measures 3.7 metres by 3.4 metres and is 0.8 metres thick, supported by a southern portal stone standing 1.6 metres high. Nearby lies what may be a collapsed door stone, a slab that would originally have sealed the chamber entrance, along with two smaller upright stones.

The tomb sits in a slight col, a shallow saddle of land between higher ground, with Cairnhill rising to around 180 metres to the south and a ridge some 120 metres to the north. To the west and east the land drops away, and two streams run roughly north to south before joining approximately 700 metres to the south. This kind of carefully chosen position, neither at a summit nor tucked into a valley, is a feature seen at other Neolithic monuments across Ireland, where builders seem to have favoured places that commanded sight lines without fully exposing the structure to the elements. The monument sits just to the western side of a field bank running roughly north-north-west to south-south-east, a boundary that may itself be ancient, or may simply have grown up around the stones over the centuries. The site was recorded by George Eogan in 1958 and later referenced by Seán Ó Nualláin in 1983, two researchers who documented portal tombs systematically across the island during the mid to late twentieth century.