It is easy to miss, which is part of what makes it quietly remarkable. The earthwork measures roughly 32 metres north to south and 29 metres east to west, making it a modest but coherent space, ringed by a bank of earth and stone that barely reaches 30 centimetres in height and a shallow external fosse, or ditch, about four metres wide. These are not the dramatic ramparts of a hill fort; this is something more ordinary, and in its ordinariness, more revealing.

This is a rath, a type of enclosed farmstead common across early medieval Ireland, typically dating from roughly the fifth to the twelfth century. Raths are among the most numerous field monuments in the country, with tens of thousands once dotting the landscape, though many have been lost to ploughing, development, and the slow levelling of time. The defining feature is a circular or near-circular bank, sometimes accompanied by a ditch on the outside, enclosing a domestic space where a farming family would have kept their animals at night and gone about the business of daily life. The example at Knockaculleen is unassuming even by rath standards; its bank has settled to a height of only 0.3 metres, the fosse barely registers as a depression, and no trace of the original entrance survives to indicate which direction the occupants faced the world.