This is a ring barrow, a type of Bronze Age funerary monument in which a burial, or sometimes several, was placed within a roughly circular enclosure defined by a surrounding fosse (a cut ditch) and an accompanying bank. The form is common enough across Ireland, but each example is its own small argument against the idea that ancient landscapes have been entirely erased.

The barrow at Barr An tSeanchnoic measures fifteen metres across in both directions, making it a near-perfect circle. Its fosse is V-shaped in cross-section, roughly a metre deep and three metres wide, with the external bank running from the east around to the north and rising to about forty centimetres. The bank is now heavily colonised by gorse, and the interior is slightly raised, as one would expect where a mound has settled and compacted over centuries. A roadway has clipped the northeastern edge, truncating the bank at that point and offering an inadvertent cross-section of the monument's construction. That kind of damage is common, accumulating over generations of agricultural use, road improvements, and general indifference to anything that looks, from a distance, like an unremarkable rise in a field.