The site at Killeen in County Galway appears on the third edition of the Ordnance Survey six-inch map, published in 1946, as a D-shaped hollow running roughly northwest to southeast and measuring around twenty metres across. That hollow, sitting on the north side of a roadside in undulating grassland, was enough of a landmark that people in the area continued to associate it with a fort long after any obvious structure had gone.

The feature was almost certainly the remains of a rath, the Irish term for a ringfort, which was the most common form of rural settlement in early medieval Ireland, typically consisting of a circular or near-circular enclosure defined by an earthen bank and ditch. Thousands survive across the country in varying states of preservation, but many others have been erased by agriculture, development, or simple erosion over the centuries. The D-shaped outline recorded at Killeen suggests the earthwork had already been significantly reduced by the time cartographers noted it, leaving only a faint depression in the ground where the enclosure once stood. At some point after 1946, a house was built on the site, completing the transformation from early medieval settlement to modern domestic plot.