It is a rath, the Irish term for a ringfort, which was the standard form of enclosed farmstead used across Ireland from roughly the early medieval period. Most raths were built and occupied between about 500 and 1000 AD, and tens of thousands of them survive in varying states across the country. This one, measuring approximately 28 metres in diameter, is defined by a low earthen bank rising to about 0.8 metres, overgrown enough that its circular shape is more legible on a map than from the ground.

Ordnance Survey maps from 1846 and from the 1893 to 1894 revision both record it as a circular enclosure, though at a slightly larger diameter of around 35 metres, suggesting some shrinkage or erosion in the intervening period. There is visible erosion along the north-eastern section of the bank, and a mound of earth has been piled against the outer face on the southern side, possibly the result of clearance activity associated with the surrounding industrial use. The concrete yard that now extends to the base of the bank is a reasonable shorthand for the site's current situation: a prehistoric or early medieval domestic enclosure that has quietly survived, in diminished form, inside a working industrial zone.

Access is restricted and the interior is described as inaccessible, so this is not a place that rewards a visit in the usual sense. What it does offer is a particular kind of historical irony. The rath at Teernaboul persists not because it was protected or celebrated, but simply because it was awkward to remove entirely. The bank endures at less than a metre high, the enclosure overgrown, the original entrance long since lost, while the yard around it gets on with its business.