This is a ring barrow, a type of prehistoric funerary monument consisting of a central area enclosed by a bank and an outer ditch, and the example at Clashganniv is modest but intact enough to read. The enclosed space measures roughly 24.8 metres northeast to southwest and 23.8 metres northwest to southeast, making it a reasonably substantial feature for something so easy to walk past without recognition.

The surrounding fosse, a shallow ditch that in this case has become marshy, runs to a depth of around 0.25 metres, and a low bank survives along the northeastern to east-southeastern arc and again from the south-southwest to the west-northwest. The northwestern portion of the bank has been cut away by the stream and a drainage channel associated with it, which accounts for the gap in what would otherwise have been a near-complete circuit. Ring barrows belong broadly to the Bronze Age, though the tradition of constructing earthen enclosures around burial sites spans a long period in Irish prehistory, and without excavation it is difficult to date any individual example precisely. The marshy character of the fosse here suggests that the low-lying streamside location has always made this a damp spot, which may itself have carried meaning for the people who chose it.