One hundred and nine timber posts are set into the lake bed, rising only about thirty centimetres above the sediment, yet together they trace a route ninety metres long and nine metres wide from east to west. That is roughly the width of a modest road and the length of nearly a third of a football pitch, held in place by posts that have sat in the water long enough to become archaeology.

The posts sit just to the east of an existing causeway, suggesting the modern crossing and the ancient one share the same logic, the same geography, the same need to get from one side to the other at the point where the lake narrows enough to make it possible. Lough Carra is a shallow, marl-bottomed lake, its pale limestone-filtered water giving it an unusual milky-green tint, and its bed preserves organic material unusually well. That quality of preservation is likely why the timber posts have survived at all. The structure was recorded as part of a survey of Ballinrobe and district compiled by D. Lavelle and published in 1994 by the Lough Mask and Lough Carra Tourist Development Association, though the posts themselves belong to a much older moment, the precise date of which remains unestablished in the available record.

The site is submerged and not directly accessible to a casual visitor on foot, but the causeway that stands beside it offers a natural vantage point over the neck of water where the posts lie. Lough Carra is calm enough on still days that the shallow bed is occasionally visible, and knowing that more than a hundred upright timbers are arranged just below the surface changes how you look at even an unremarkable stretch of lake.