The structure runs 124 metres from west to east and measures between two and four metres wide, with the posts arranged in a roughly double row at each end and clustering more densely at the midpoint. It is the kind of thing that is easy to pass over entirely, since nothing of it is visible above water, yet it represents a deliberate, carefully organised piece of engineering from a period most people associate with little more than standing stones and hillforts.

Radiocarbon dating of two oak samples has produced results that are striking precisely because of how far apart they are. One sample returned an estimated felling date of 1539 plus or minus nine years BC, placing it solidly in the Middle Bronze Age. The other gave a felling date of 1069 plus or minus nine years BC, towards the end of the Late Bronze Age. The gap between those two dates is roughly five centuries, which raises the question of whether the causeway was constructed in stages, repaired substantially at some later point, or whether the timbers simply represent different phases of use. Both samples were identified as indigenous oak, the dominant timber used in Irish prehistoric construction, valued for its durability even in waterlogged conditions. The causeway sits in what would have been a strategically useful crossing point on Lough Carra, a lake known for its shallow, marl-rich waters and relatively low visibility, which may partly explain why the posts have survived at all.