They exist, as far as current knowledge goes, only as dark rings on an aerial photograph, crop marks betraying the faint outlines of prehistoric ditches pressed into the soil beneath a field.

A ring-ditch is exactly what it sounds like: a circular ditch, usually dug in prehistory, sometimes surrounding a burial mound that has long since been ploughed or eroded flat. At Flemby, there are three of them arranged in a loose line, each roughly 25 metres from the next, with diameters ranging from about 10 to 18 metres. The site sits on level but slightly marshy ground at the base of the hills that form the eastern end of Sliabh Mis, and from it there are clear sightlines north towards the Stacks Mountains. That positioning may or may not be coincidental; prehistoric monument builders frequently chose sites with particular landscape orientations, though without excavation it is impossible to say what the Flemby ditches contained or when exactly they were made. The site was identified and described by Michael Connolly in his 2008 doctoral thesis on prehistoric settlement in the Lee Valley near Tralee, a study that drew extensively on aerial photographic evidence to locate sites of this kind that ground-level survey would simply miss.

Crop marks like these appear when buried features affect the growth of grass or cereal crops above them, producing subtle differences in colour and height that only become legible from the air under the right lighting and at the right time of year. The three rings at Flemby are currently known only from that photographic record. Whether anything survives below the surface intact, and what relationship the three enclosures bear to one another, remain open questions.