Others exist mainly as a ring on a photograph taken from the air, invisible to anyone standing in the field above them. The possible rath at Lissyviggeen in County Kerry belongs firmly to the second category. Captured on an aerial photograph in 1989, the circular enclosure, roughly 25 metres in diameter, showed up clearly enough from altitude, but on the ground it has been swallowed by dense fern growth, its outline surviving only as an unevenness underfoot.

A rath is an early medieval ringfort, typically a farmstead enclosed by one or more earthen banks and ditches, and they are among the most common monument types in the Irish countryside. Thousands survive across the island, though many, like this one, exist in a state somewhere between present and absent. The site sits on a south-west-facing slope in rough pasture, with Mangerton Mountain visible to the south. When a site inspection was carried out in 2002, the surveyor Quinn recorded a low bank still traceable along the western arc of the enclosure, which at least confirms that something is there beneath the vegetation, not merely a trick of shadow or soil variation in an old photograph.

For anyone curious enough to seek it out, the experience would be less one of looking at a monument and more one of standing in the approximate vicinity of one. The uneven ground noted during the 2002 inspection is likely the clearest indication available at surface level, the ferns having done an efficient job of concealing whatever earthwork remains beneath them.