It is anything but. The structure is a portal tomb, a form of Neolithic megalithic monument in which two tall upright portal stones frame an entrance to a small chamber, typically capped by a large roof stone. This particular example measures two metres in length and one metre in width, opens to the north-north-west, and retains its two portal stones, side stones, and back stone in very close to their original configuration. The roof stone alone has shifted, now leaning against one of the eastern side-stones rather than sitting on top, the one concession to the passage of several thousand years.

Portal tombs of this type were constructed during the Neolithic period and are found in a broad arc across Ireland and into Britain. They were burial monuments, and the characteristic raised portal stones at the entrance gave the form its name, though folklore consistently preferred more dramatic explanations, hence the widespread local name "Giant's Grave" applied to megalithic monuments across the country. The Garran example was catalogued by Seán Ó Nualláin in 1983 and described there as a nearly perfect specimen of the type. It sits on a broad east-west spur of land, and the fact that it has been absorbed into a later field bank rather than cleared away speaks to a certain pragmatic tolerance on the part of whoever laid out that boundary, working the ancient stones into the landscape rather than dismantling them.