The ring-ditch at Palmerstown is known entirely through a crop mark, one of those ghostly impressions that appear in aerial photography when buried ditches cause the vegetation above them to grow at a slightly different rate to the surrounding land, betraying the outline of structures long since levelled. What makes this particular example quietly interesting is that the aerial photograph revealed not one ring but two, concentric circles pressed into the earth, measuring 24.6 metres in diameter.

Ring-ditches are generally understood to be the eroded remnants of prehistoric funerary or ceremonial monuments, often the last surviving trace of a round barrow or burial mound whose earthen bank has been ploughed flat over centuries of farming. The double-ring form suggests the original structure may have had more complexity than a simple enclosing ditch. The site was recorded in the Sites and Monuments Record and the crop mark was identified through aerial photographic analysis, with the detail communicated by T. Condit. The record was compiled by David O'Connor and later updated by Christine Baker, with an upload date of November 2014. Beyond the aerial evidence and the approximate dimensions, the monument's date and precise function remain unexcavated questions.

The land here is relatively flat and open, with extensive views in all directions, which may itself be a clue to why someone once chose this spot for a monument. There are no visible remains on the ground whatsoever; a visitor standing in the area would see nothing out of the ordinary. The site is on arable farmland and is not publicly accessible in any formal sense. The crop mark, which is the only way this monument has ever been perceived, would require the right combination of crop type, dry conditions, and aerial vantage point to be seen again. It is, in a very real sense, a site that exists primarily as a photograph and a set of coordinates.