The rath at Ardraw, known variously as 'Ard Rath' and 'Ardagh Fort' on early Ordnance Survey records, is a bivallate example, meaning it was defended by two concentric earthen banks rather than the single bank more commonly seen. Between those banks lies a fosse, or ditch, with a V-shaped cross-section, and the inner bank still rises 4.5 metres above the base of that ditch. A causewayed entrance at the northwest breaks both banks, with gaps of 2.5 and 3 metres respectively, and the interior, roughly 24 metres across at its widest, is now thickly planted with trees. The river's natural curve would have reinforced the man-made defences on three sides, making the position a quietly considered one.

In 1904, the ground inside the western half of the rath gave way, and sections of a stone-built souterrain collapsed. A souterrain is an underground stone-lined passage, typically associated with early medieval raths and used for storage or concealment. What the collapse exposed were two passages: the larger aligned northeast to southwest, roughly 3.55 metres long, with a lintelled roof sitting about 1.6 metres below the rath's interior surface; the second, close by, a more compact chamber of around 1.2 metres square on a roughly north-south axis. By the time the Cork and Kerry Field Club documented the site in 1940, the passages had already been disturbed, the stones thrown about and the structure damaged. Among the scattered masonry was a horseshoe-shaped stone identified as likely belonging to a crawl doorway, a narrow porthole opening of the kind recorded in comparable souterrains at Kimego West and Kealduff Upper in Kerry. No trace of the souterrain is visible at the surface today.